This is the full developer documentation for Hono.
# Start of Hono documentation
# Hono
Hono - _**means flame🔥 in Japanese**_ - is a small, simple, and ultrafast web framework built on Web Standards.
It works on any JavaScript runtime: Cloudflare Workers, Fastly Compute, Deno, Bun, Vercel, Netlify, AWS Lambda, Lambda@Edge, and Node.js.
Fast, but not only fast.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
app.get('/', (c) => c.text('Hono!'))
export default app
```
## Quick Start
Just run this:
::: code-group
```sh [npm]
npm create hono@latest
```
```sh [yarn]
yarn create hono
```
```sh [pnpm]
pnpm create hono@latest
```
```sh [bun]
bun create hono@latest
```
```sh [deno]
deno init --npm hono@latest
```
:::
## Features
- **Ultrafast** 🚀 - The router `RegExpRouter` is really fast. Not using linear loops. Fast.
- **Lightweight** 🪶 - The `hono/tiny` preset is under 14kB. Hono has zero dependencies and uses only the Web Standards.
- **Multi-runtime** 🌍 - Works on Cloudflare Workers, Fastly Compute, Deno, Bun, AWS Lambda, or Node.js. The same code runs on all platforms.
- **Batteries Included** 🔋 - Hono has built-in middleware, custom middleware, third-party middleware, and helpers. Batteries included.
- **Delightful DX** 😃 - Super clean APIs. First-class TypeScript support. Now, we've got "Types".
## Use-cases
Hono is a simple web application framework similar to Express, without a frontend.
But it runs on CDN Edges and allows you to construct larger applications when combined with middleware.
Here are some examples of use-cases.
- Building Web APIs
- Proxy of backend servers
- Front of CDN
- Edge application
- Base server for a library
- Full-stack application
## Who is using Hono?
| Project | Platform | What for? |
| ---------------------------------------------------------------------------------- | ------------------ | ----------------------------------------------------------------------------------------------------------- |
| [cdnjs](https://cdnjs.com) | Cloudflare Workers | A free and open-source CDN service. _Hono is used for the API server_. |
| [Cloudflare D1](https://www.cloudflare.com/developer-platform/d1/) | Cloudflare Workers | Serverless SQL databases. _Hono is used for the internal API server_. |
| [Cloudflare Workers KV](https://www.cloudflare.com/developer-platform/workers-kv/) | Cloudflare Workers | Serverless key-value database. _Hono is used for the internal API server_. |
| [BaseAI](https://baseai.dev) | Local AI Server | Serverless AI agent pipes with memory. An open-source agentic AI framework for web. _API server with Hono_. |
| [Unkey](https://unkey.dev) | Cloudflare Workers | An open-source API authentication and authorization. _Hono is used for the API server_. |
| [OpenStatus](https://openstatus.dev) | Bun | An open-source website & API monitoring platform. _Hono is used for the API server_. |
| [Deno Benchmarks](https://deno.com/benchmarks) | Deno | A secure TypeScript runtime built on V8. _Hono is used for benchmarking_. |
And the following.
- [Drivly](https://driv.ly/) - Cloudflare Workers
- [repeat.dev](https://repeat.dev/) - Cloudflare Workers
Do you want to see more? See [Who is using Hono in production?](https://github.com/orgs/honojs/discussions/1510).
## Hono in 1 minute
A demonstration to create an application for Cloudflare Workers with Hono.
## Ultrafast
**Hono is the fastest**, compared to other routers for Cloudflare Workers.
```
Hono x 402,820 ops/sec ±4.78% (80 runs sampled)
itty-router x 212,598 ops/sec ±3.11% (87 runs sampled)
sunder x 297,036 ops/sec ±4.76% (77 runs sampled)
worktop x 197,345 ops/sec ±2.40% (88 runs sampled)
Fastest is Hono
✨ Done in 28.06s.
```
See [more benchmarks](/docs/concepts/benchmarks).
## Lightweight
**Hono is so small**. With the `hono/tiny` preset, its size is **under 14KB** when minified. There are many middleware and adapters, but they are bundled only when used. For context, the size of Express is 572KB.
```
$ npx wrangler dev --minify ./src/index.ts
⛅️ wrangler 2.20.0
--------------------
⬣ Listening at http://0.0.0.0:8787
- http://127.0.0.1:8787
- http://192.168.128.165:8787
Total Upload: 11.47 KiB / gzip: 4.34 KiB
```
## Multiple routers
**Hono has multiple routers**.
**RegExpRouter** is the fastest router in the JavaScript world. It matches the route using a single large Regex created before dispatch. With **SmartRouter**, it supports all route patterns.
**LinearRouter** registers the routes very quickly, so it's suitable for an environment that initializes applications every time. **PatternRouter** simply adds and matches the pattern, making it small.
See [more information about routes](/docs/concepts/routers).
## Web Standards
Thanks to the use of the **Web Standards**, Hono works on a lot of platforms.
- Cloudflare Workers
- Cloudflare Pages
- Fastly Compute
- Deno
- Bun
- Vercel
- AWS Lambda
- Lambda@Edge
- Others
And by using [a Node.js adapter](https://github.com/honojs/node-server), Hono works on Node.js.
See [more information about Web Standards](/docs/concepts/web-standard).
## Middleware & Helpers
**Hono has many middleware and helpers**. This makes "Write Less, do more" a reality.
Out of the box, Hono provides middleware and helpers for:
- [Basic Authentication](/docs/middleware/builtin/basic-auth)
- [Bearer Authentication](/docs/middleware/builtin/bearer-auth)
- [Body Limit](/docs/middleware/builtin/body-limit)
- [Cache](/docs/middleware/builtin/cache)
- [Compress](/docs/middleware/builtin/compress)
- [Context Storage](/docs/middleware/builtin/context-storage)
- [Cookie](/docs/helpers/cookie)
- [CORS](/docs/middleware/builtin/cors)
- [ETag](/docs/middleware/builtin/etag)
- [html](/docs/helpers/html)
- [JSX](/docs/guides/jsx)
- [JWT Authentication](/docs/middleware/builtin/jwt)
- [Logger](/docs/middleware/builtin/logger)
- [Language](/docs/middleware/builtin/language)
- [Pretty JSON](/docs/middleware/builtin/pretty-json)
- [Secure Headers](/docs/middleware/builtin/secure-headers)
- [SSG](/docs/helpers/ssg)
- [Streaming](/docs/helpers/streaming)
- [GraphQL Server](https://github.com/honojs/middleware/tree/main/packages/graphql-server)
- [Firebase Authentication](https://github.com/honojs/middleware/tree/main/packages/firebase-auth)
- [Sentry](https://github.com/honojs/middleware/tree/main/packages/sentry)
- Others!
For example, adding ETag and request logging only takes a few lines of code with Hono:
```ts
import { Hono } from 'hono'
import { etag } from 'hono/etag'
import { logger } from 'hono/logger'
const app = new Hono()
app.use(etag(), logger())
```
See [more information about Middleware](/docs/concepts/middleware).
## Developer Experience
Hono provides a delightful "**Developer Experience**".
Easy access to Request/Response thanks to the `Context` object.
Moreover, Hono is written in TypeScript. Hono has "**Types**".
For example, the path parameters will be literal types.
And, the Validator and Hono Client `hc` enable the RPC mode. In RPC mode,
you can use your favorite validator such as Zod and easily share server-side API specs with the client and build type-safe applications.
See [Hono Stacks](/docs/concepts/stacks).
# Third-party Middleware
Third-party middleware refers to middleware not bundled within the Hono package.
Most of this middleware leverages external libraries.
### Authentication
- [Auth.js(Next Auth)](https://github.com/honojs/middleware/tree/main/packages/auth-js)
- [Clerk Auth](https://github.com/honojs/middleware/tree/main/packages/clerk-auth)
- [OAuth Providers](https://github.com/honojs/middleware/tree/main/packages/oauth-providers)
- [OIDC Auth](https://github.com/honojs/middleware/tree/main/packages/oidc-auth)
- [Firebase Auth](https://github.com/honojs/middleware/tree/main/packages/firebase-auth)
- [Verify RSA JWT (JWKS)](https://github.com/wataruoguchi/verify-rsa-jwt-cloudflare-worker)
### Validators
- [ArkType validator](https://github.com/honojs/middleware/tree/main/packages/arktype-validator)
- [Effect Schema Validator](https://github.com/honojs/middleware/tree/main/packages/effect-validator)
- [Standard Schema Validator](https://github.com/honojs/middleware/tree/main/packages/standard-validator)
- [TypeBox Validator](https://github.com/honojs/middleware/tree/main/packages/typebox-validator)
- [Typia Validator](https://github.com/honojs/middleware/tree/main/packages/typia-validator)
- [unknownutil Validator](https://github.com/ryoppippi/hono-unknownutil-validator)
- [Valibot Validator](https://github.com/honojs/middleware/tree/main/packages/valibot-validator)
- [Zod Validator](https://github.com/honojs/middleware/tree/main/packages/zod-validator)
### OpenAPI
- [Zod OpenAPI](https://github.com/honojs/middleware/tree/main/packages/zod-openapi)
- [Scalar API Reference](https://github.com/scalar/scalar/tree/main/integrations/hono)
- [Swagger UI](https://github.com/honojs/middleware/tree/main/packages/swagger-ui)
- [Hono OpenAPI](https://github.com/rhinobase/hono-openapi)
### Others
- [Bun Transpiler](https://github.com/honojs/middleware/tree/main/packages/bun-transpiler)
- [esbuild Transpiler](https://github.com/honojs/middleware/tree/main/packages/esbuild-transpiler)
- [Event Emitter](https://github.com/honojs/middleware/tree/main/packages/event-emitter)
- [GraphQL Server](https://github.com/honojs/middleware/tree/main/packages/graphql-server)
- [Hono Rate Limiter](https://github.com/rhinobase/hono-rate-limiter)
- [Node WebSocket Helper](https://github.com/honojs/middleware/tree/main/packages/node-ws)
- [Prometheus Metrics](https://github.com/honojs/middleware/tree/main/packages/prometheus)
- [Qwik City](https://github.com/honojs/middleware/tree/main/packages/qwik-city)
- [React Compatibility](https://github.com/honojs/middleware/tree/main/packages/react-compat)
- [React Renderer](https://github.com/honojs/middleware/tree/main/packages/react-renderer)
- [RONIN (Database)](https://github.com/ronin-co/hono-client)
- [Sentry](https://github.com/honojs/middleware/tree/main/packages/sentry)
- [tRPC Server](https://github.com/honojs/middleware/tree/main/packages/trpc-server)
- [Geo](https://github.com/ktkongtong/hono-geo-middleware/tree/main/packages/middleware)
- [Hono Simple DI](https://github.com/maou-shonen/hono-simple-DI)
- [Highlight.io](https://www.highlight.io/docs/getting-started/backend-sdk/js/hono)
# Basic Auth Middleware
This middleware can apply Basic authentication to a specified path.
Implementing Basic authentication with Cloudflare Workers or other platforms is more complicated than it seems, but with this middleware, it's a breeze.
For more information about how the Basic auth scheme works under the hood, see the [MDN docs](https://developer.mozilla.org/en-US/docs/Web/HTTP/Authentication#basic_authentication_scheme).
## Import
```ts
import { Hono } from 'hono'
import { basicAuth } from 'hono/basic-auth'
```
## Usage
```ts
const app = new Hono()
app.use(
'/auth/*',
basicAuth({
username: 'hono',
password: 'acoolproject',
})
)
app.get('/auth/page', (c) => {
return c.text('You are authorized')
})
```
To restrict to a specific route + method:
```ts
const app = new Hono()
app.get('/auth/page', (c) => {
return c.text('Viewing page')
})
app.delete(
'/auth/page',
basicAuth({ username: 'hono', password: 'acoolproject' }),
(c) => {
return c.text('Page deleted')
}
)
```
If you want to verify the user by yourself, specify the `verifyUser` option; returning `true` means it is accepted.
```ts
const app = new Hono()
app.use(
basicAuth({
verifyUser: (username, password, c) => {
return (
username === 'dynamic-user' && password === 'hono-password'
)
},
})
)
```
## Options
### username: `string`
The username of the user who is authenticating.
### password: `string`
The password value for the provided username to authenticate against.
### realm: `string`
The domain name of the realm, as part of the returned WWW-Authenticate challenge header. The default is `"Secure Area"`.
See more: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/WWW-Authenticate#directives
### hashFunction: `Function`
A function to handle hashing for safe comparison of passwords.
### verifyUser: `(username: string, password: string, c: Context) => boolean | Promise`
The function to verify the user.
### invalidUserMessage: `string | object | MessageFunction`
`MessageFunction` is `(c: Context) => string | object | Promise`. The custom message if the user is invalid.
## More Options
### ...users: `{ username: string, password: string }[]`
## Recipes
### Defining Multiple Users
This middleware also allows you to pass arbitrary parameters containing objects defining more `username` and `password` pairs.
```ts
app.use(
'/auth/*',
basicAuth(
{
username: 'hono',
password: 'acoolproject',
// Define other params in the first object
realm: 'www.example.com',
},
{
username: 'hono-admin',
password: 'super-secure',
// Cannot redefine other params here
},
{
username: 'hono-user-1',
password: 'a-secret',
// Or here
}
)
)
```
Or less hardcoded:
```ts
import { users } from '../config/users'
app.use(
'/auth/*',
basicAuth(
{
realm: 'www.example.com',
...users[0],
},
...users.slice(1)
)
)
```
# Bearer Auth Middleware
The Bearer Auth Middleware provides authentication by verifying an API token in the Request header.
The HTTP clients accessing the endpoint will add the `Authorization` header with `Bearer {token}` as the header value.
Using `curl` from the terminal, it would look like this:
```sh
curl -H 'Authorization: Bearer honoiscool' http://localhost:8787/auth/page
```
## Import
```ts
import { Hono } from 'hono'
import { bearerAuth } from 'hono/bearer-auth'
```
## Usage
> [!NOTE]
> Your `token` must match the regex `/[A-Za-z0-9._~+/-]+=*/`, otherwise a 400 error will be returned. Notably, this regex acommodates both URL-safe Base64- and standard Base64-encoded JWTs. This middleware does not require the bearer token to be a JWT, just that it matches the above regex.
```ts
const app = new Hono()
const token = 'honoiscool'
app.use('/api/*', bearerAuth({ token }))
app.get('/api/page', (c) => {
return c.json({ message: 'You are authorized' })
})
```
To restrict to a specific route + method:
```ts
const app = new Hono()
const token = 'honoiscool'
app.get('/api/page', (c) => {
return c.json({ message: 'Read posts' })
})
app.post('/api/page', bearerAuth({ token }), (c) => {
return c.json({ message: 'Created post!' }, 201)
})
```
To implement multiple tokens (E.g., any valid token can read but create/update/delete are restricted to a privileged token):
```ts
const app = new Hono()
const readToken = 'read'
const privilegedToken = 'read+write'
const privilegedMethods = ['POST', 'PUT', 'PATCH', 'DELETE']
app.on('GET', '/api/page/*', async (c, next) => {
// List of valid tokens
const bearer = bearerAuth({ token: [readToken, privilegedToken] })
return bearer(c, next)
})
app.on(privilegedMethods, '/api/page/*', async (c, next) => {
// Single valid privileged token
const bearer = bearerAuth({ token: privilegedToken })
return bearer(c, next)
})
// Define handlers for GET, POST, etc.
```
If you want to verify the value of the token yourself, specify the `verifyToken` option; returning `true` means it is accepted.
```ts
const app = new Hono()
app.use(
'/auth-verify-token/*',
bearerAuth({
verifyToken: async (token, c) => {
return token === 'dynamic-token'
},
})
)
```
## Options
### token: `string` | `string[]`
The string to validate the incoming bearer token against.
### realm: `string`
The domain name of the realm, as part of the returned WWW-Authenticate challenge header. The default is `""`.
See more: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/WWW-Authenticate#directives
### prefix: `string`
The prefix (or known as `schema`) for the Authorization header value. The default is `"Bearer"`.
### headerName: `string`
The header name. The default value is `Authorization`.
### hashFunction: `Function`
A function to handle hashing for safe comparison of authentication tokens.
### verifyToken: `(token: string, c: Context) => boolean | Promise`
The function to verify the token.
### noAuthenticationHeaderMessage: `string | object | MessageFunction`
`MessageFunction` is `(c: Context) => string | object | Promise`. The custom message if it does not have an authentication header.
### invalidAuthenticationHeaderMessage: `string | object | MessageFunction`
The custom message if the authentication header is invalid.
### invalidTokenMessage: `string | object | MessageFunction`
The custom message if the token is invalid.
# Body Limit Middleware
The Body Limit Middleware can limit the file size of the request body.
This middleware first uses the value of the `Content-Length` header in the request, if present.
If it is not set, it reads the body in the stream and executes an error handler if it is larger than the specified file size.
## Import
```ts
import { Hono } from 'hono'
import { bodyLimit } from 'hono/body-limit'
```
## Usage
```ts
const app = new Hono()
app.post(
'/upload',
bodyLimit({
maxSize: 50 * 1024, // 50kb
onError: (c) => {
return c.text('overflow :(', 413)
},
}),
async (c) => {
const body = await c.req.parseBody()
if (body['file'] instanceof File) {
console.log(`Got file sized: ${body['file'].size}`)
}
return c.text('pass :)')
}
)
```
## Options
### maxSize: `number`
The maximum file size of the file you want to limit. The default is `100 * 1024` - `100kb`.
### onError: `OnError`
The error handler to be invoked if the specified file size is exceeded.
## Usage with Bun for large requests
If the Body Limit Middleware is used explicitly to allow a request body larger than the default, it might be necessary to make changes to your `Bun.serve` configuration accordingly. [At the time of writing](https://github.com/oven-sh/bun/blob/f2cfa15e4ef9d730fc6842ad8b79fb7ab4c71cb9/packages/bun-types/bun.d.ts#L2191), `Bun.serve`'s default request body limit is 128MiB. If you set Hono's Body Limit Middleware to a value bigger than that, your requests will still fail and, additionally, the `onError` handler specified in the middleware will not be called. This is because `Bun.serve()` will set the status code to `413` and terminate the connection before passing the request to Hono.
If you want to accept requests larger than 128MiB with Hono and Bun, you need to set the limit for Bun as well:
```ts
export default {
port: process.env['PORT'] || 3000,
fetch: app.fetch,
maxRequestBodySize: 1024 * 1024 * 200, // your value here
}
```
or, depending on your setup:
```ts
Bun.serve({
fetch(req, server) {
return app.fetch(req, { ip: server.requestIP(req) })
},
maxRequestBodySize: 1024 * 1024 * 200, // your value here
})
```
# Cache Middleware
The Cache middleware uses the Web Standards' [Cache API](https://developer.mozilla.org/en-US/docs/Web/API/Cache).
The Cache middleware currently supports Cloudflare Workers projects using custom domains and Deno projects using [Deno 1.26+](https://github.com/denoland/deno/releases/tag/v1.26.0). Also available with Deno Deploy.
Cloudflare Workers respects the `Cache-Control` header and return cached responses. For details, refer to [Cache on Cloudflare Docs](https://developers.cloudflare.com/workers/runtime-apis/cache/). Deno does not respect headers, so if you need to update the cache, you will need to implement your own mechanism.
See [Usage](#usage) below for instructions on each platform.
## Import
```ts
import { Hono } from 'hono'
import { cache } from 'hono/cache'
```
## Usage
::: code-group
```ts [Cloudflare Workers]
app.get(
'*',
cache({
cacheName: 'my-app',
cacheControl: 'max-age=3600',
})
)
```
```ts [Deno]
// Must use `wait: true` for the Deno runtime
app.get(
'*',
cache({
cacheName: 'my-app',
cacheControl: 'max-age=3600',
wait: true,
})
)
```
:::
## Options
### cacheName: `string` | `(c: Context) => string` | `Promise`
The name of the cache. Can be used to store multiple caches with different identifiers.
### wait: `boolean`
A boolean indicating if Hono should wait for the Promise of the `cache.put` function to resolve before continuing with the request. _Required to be true for the Deno environment_. The default is `false`.
### cacheControl: `string`
A string of directives for the `Cache-Control` header. See the [MDN docs](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control) for more information. When this option is not provided, no `Cache-Control` header is added to requests.
### vary: `string` | `string[]`
Sets the `Vary` header in the response. If the original response header already contains a `Vary` header, the values are merged, removing any duplicates. Setting this to `*` will result in an error. For more details on the Vary header and its implications for caching strategies, refer to the [MDN docs](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Vary).
### keyGenerator: `(c: Context) => string | Promise`
Generates keys for every request in the `cacheName` store. This can be used to cache data based on request parameters or context parameters. The default is `c.req.url`.
# Combine Middleware
Combine Middleware combines multiple middleware functions into a single middleware. It provides three functions:
- `some` - Runs only one of the given middleware.
- `every` - Runs all given middleware.
- `except` - Runs all given middleware only if a condition is not met.
## Import
```ts
import { Hono } from 'hono'
import { some, every, except } from 'hono/combine'
```
## Usage
Here's an example of complex access control rules using Combine Middleware.
```ts
import { Hono } from 'hono'
import { bearerAuth } from 'hono/bearer-auth'
import { getConnInfo } from 'hono/cloudflare-workers'
import { every, some } from 'hono/combine'
import { ipRestriction } from 'hono/ip-restriction'
import { rateLimit } from '@/my-rate-limit'
const app = new Hono()
app.use(
'*',
some(
every(
ipRestriction(getConnInfo, { allowList: ['192.168.0.2'] }),
bearerAuth({ token })
),
// If both conditions are met, rateLimit will not execute.
rateLimit()
)
)
app.get('/', (c) => c.text('Hello Hono!'))
```
### some
Runs the first middleware that returns true. Middleware is applied in order, and if any middleware exits successfully, subsequent middleware will not run.
```ts
import { some } from 'hono/combine'
import { bearerAuth } from 'hono/bearer-auth'
import { myRateLimit } from '@/rate-limit'
// If client has a valid token, skip rate limiting.
// Otherwise, apply rate limiting.
app.use(
'/api/*',
some(bearerAuth({ token }), myRateLimit({ limit: 100 }))
)
```
### every
Runs all middleware and stops if any of them fail. Middleware is applied in order, and if any middleware throws an error, subsequent middleware will not run.
```ts
import { some, every } from 'hono/combine'
import { bearerAuth } from 'hono/bearer-auth'
import { myCheckLocalNetwork } from '@/check-local-network'
import { myRateLimit } from '@/rate-limit'
// If client is in local network, skip authentication and rate limiting.
// Otherwise, apply authentication and rate limiting.
app.use(
'/api/*',
some(
myCheckLocalNetwork(),
every(bearerAuth({ token }), myRateLimit({ limit: 100 }))
)
)
```
### except
Runs all middleware except when the condition is met. You can pass a string or function as the condition. If multiple targets need to be matched, pass them as an array.
```ts
import { except } from 'hono/combine'
import { bearerAuth } from 'hono/bearer-auth'
// If client is accessing public API, skip authentication.
// Otherwise, require a valid token.
app.use('/api/*', except('/api/public/*', bearerAuth({ token })))
```
# Compress Middleware
This middleware compresses the response body, according to `Accept-Encoding` request header.
::: info
**Note**: On Cloudflare Workers and Deno Deploy, the response body will be compressed automatically, so there is no need to use this middleware.
**Bun**: This middleware uses `CompressionStream` which is not yet supported in bun.
:::
## Import
```ts
import { Hono } from 'hono'
import { compress } from 'hono/compress'
```
## Usage
```ts
const app = new Hono()
app.use(compress())
```
## Options
### encoding: `'gzip'` | `'deflate'`
The compression scheme to allow for response compression. Either `gzip` or `deflate`. If not defined, both are allowed and will be used based on the `Accept-Encoding` header. `gzip` is prioritized if this option is not provided and the client provides both in the `Accept-Encoding` header.
### threshold: `number`
The minimum size in bytes to compress. Defaults to 1024 bytes.
# Context Storage Middleware
The Context Storage Middleware stores the Hono `Context` in the `AsyncLocalStorage`, to make it globally accessible.
::: info
**Note** This middleware uses `AsyncLocalStorage`. The runtime should support it.
**Cloudflare Workers**: To enable `AsyncLocalStorage`, add the [`nodejs_compat` or `nodejs_als` flag](https://developers.cloudflare.com/workers/configuration/compatibility-dates/#nodejs-compatibility-flag) to your `wrangler.toml` file.
:::
## Import
```ts
import { Hono } from 'hono'
import { contextStorage, getContext } from 'hono/context-storage'
```
## Usage
The `getContext()` will return the current Context object if the `contextStorage()` is applied as a middleware.
```ts
type Env = {
Variables: {
message: string
}
}
const app = new Hono()
app.use(contextStorage())
app.use(async (c, next) => {
c.set('message', 'Hello!')
await next()
})
// You can access the variable outside the handler.
const getMessage = () => {
return getContext().var.message
}
app.get('/', (c) => {
return c.text(getMessage())
})
```
On Cloudflare Workers, you can access the bindings outside the handler.
```ts
type Env = {
Bindings: {
KV: KVNamespace
}
}
const app = new Hono()
app.use(contextStorage())
const setKV = (value: string) => {
return getContext().env.KV.put('key', value)
}
```
# CORS Middleware
There are many use cases of Cloudflare Workers as Web APIs and calling them from external front-end application.
For them we have to implement CORS, let's do this with middleware as well.
## Import
```ts
import { Hono } from 'hono'
import { cors } from 'hono/cors'
```
## Usage
```ts
const app = new Hono()
// CORS should be called before the route
app.use('/api/*', cors())
app.use(
'/api2/*',
cors({
origin: 'http://example.com',
allowHeaders: ['X-Custom-Header', 'Upgrade-Insecure-Requests'],
allowMethods: ['POST', 'GET', 'OPTIONS'],
exposeHeaders: ['Content-Length', 'X-Kuma-Revision'],
maxAge: 600,
credentials: true,
})
)
app.all('/api/abc', (c) => {
return c.json({ success: true })
})
app.all('/api2/abc', (c) => {
return c.json({ success: true })
})
```
Multiple origins:
```ts
app.use(
'/api3/*',
cors({
origin: ['https://example.com', 'https://example.org'],
})
)
// Or you can use "function"
app.use(
'/api4/*',
cors({
// `c` is a `Context` object
origin: (origin, c) => {
return origin.endsWith('.example.com')
? origin
: 'http://example.com'
},
})
)
```
## Options
### origin: `string` | `string[]` | `(origin:string, c:Context) => string`
The value of "_Access-Control-Allow-Origin_" CORS header. You can also pass the callback function like `origin: (origin) => (origin.endsWith('.example.com') ? origin : 'http://example.com')`. The default is `*`.
### allowMethods: `string[]`
The value of "_Access-Control-Allow-Methods_" CORS header. The default is `['GET', 'HEAD', 'PUT', 'POST', 'DELETE', 'PATCH']`.
### allowHeaders: `string[]`
The value of "_Access-Control-Allow-Headers_" CORS header. The default is `[]`.
### maxAge: `number`
The value of "_Access-Control-Max-Age_" CORS header.
### credentials: `boolean`
The value of "_Access-Control-Allow-Credentials_" CORS header.
### exposeHeaders: `string[]`
The value of "_Access-Control-Expose-Headers_" CORS header. The default is `[]`.
## Environment-dependent CORS configuration
If you want to adjust CORS configuration according to the execution environment, such as development or production, injecting values from environment variables is convenient as it eliminates the need for the application to be aware of its own execution environment. See the example below for clarification.
```ts
app.use('*', async (c, next) => {
const corsMiddlewareHandler = cors({
origin: c.env.CORS_ORIGIN,
})
return corsMiddlewareHandler(c, next)
})
```
# CSRF Protection
CSRF Protection Middleware prevents CSRF attacks by checking request headers.
This middleware protects against CSRF attacks such as submitting with a form element by comparing the value of the `Origin` header with the requested URL.
Old browsers that do not send `Origin` headers, or environments that use reverse proxies to remove `Origin` headers, may not work well. In such environments, use the other CSRF token methods.
## Import
```ts
import { Hono } from 'hono'
import { csrf } from 'hono/csrf'
```
## Usage
```ts
const app = new Hono()
app.use(csrf())
// Specifying origins with using `origin` option
// string
app.use(csrf({ origin: 'myapp.example.com' }))
// string[]
app.use(
csrf({
origin: ['myapp.example.com', 'development.myapp.example.com'],
})
)
// Function
// It is strongly recommended that the protocol be verified to ensure a match to `$`.
// You should *never* do a forward match.
app.use(
'*',
csrf({
origin: (origin) =>
/https:\/\/(\w+\.)?myapp\.example\.com$/.test(origin),
})
)
```
## Options
### origin: `string` | `string[]` | `Function`
Specify origins.
# ETag Middleware
Using this middleware, you can add ETag headers easily.
## Import
```ts
import { Hono } from 'hono'
import { etag } from 'hono/etag'
```
## Usage
```ts
const app = new Hono()
app.use('/etag/*', etag())
app.get('/etag/abc', (c) => {
return c.text('Hono is cool')
})
```
## The retained headers
The 304 Response must include the headers that would have been sent in an equivalent 200 OK response. The default headers are Cache-Control, Content-Location, Date, ETag, Expires, and Vary.
If you want to add the header that is sent, you can use `retainedHeaders` option and `RETAINED_304_HEADERS` strings array variable that includes the default headers:
```ts
import { etag, RETAINED_304_HEADERS } from 'hono/etag'
// ...
app.use(
'/etag/*',
etag({
retainedHeaders: ['x-message', ...RETAINED_304_HEADERS],
})
)
```
## Options
### weak: `boolean`
Define using or not using a [weak validation](https://developer.mozilla.org/en-US/docs/Web/HTTP/Conditional_requests#weak_validation). If `true` is set, then `w/` is added to the prefix of the value. The default is `false`.
### retainedHeaders: `string[]`
The headers that you want to retain in the 304 Response.
### generateDigest: `(body: Uint8Array) => ArrayBuffer | Promise`
A custom digest generation function. By default, it uses `SHA-1`. This function is called with the response body as a `Uint8Array` and should return a hash as an `ArrayBuffer` or a Promise of one.
# IP Restriction Middleware
IP Restriction Middleware is middleware that limits access to resources based on the IP address of the user.
## Import
```ts
import { Hono } from 'hono'
import { ipRestriction } from 'hono/ip-restriction'
```
## Usage
For your application running on Bun, if you want to allow access only from local, you can write it as follows. Specify the rules you want to deny in the `denyList` and the rules you want to allow in the `allowList`.
```ts
import { Hono } from 'hono'
import { getConnInfo } from 'hono/bun'
import { ipRestriction } from 'hono/ip-restriction'
const app = new Hono()
app.use(
'*',
ipRestriction(getConnInfo, {
denyList: [],
allowList: ['127.0.0.1', '::1'],
})
)
app.get('/', (c) => c.text('Hello Hono!'))
```
Pass the `getConninfo` from the [ConnInfo helper](/docs/helpers/conninfo) appropriate for your environment as the first argument of `ipRestriction`. For example, for Deno, it would look like this:
```ts
import { getConnInfo } from 'hono/deno'
import { ipRestriction } from 'hono/ip-restriction'
//...
app.use(
'*',
ipRestriction(getConnInfo, {
// ...
})
)
```
## Rules
Follow the instructions below for writing rules.
### IPv4
- `192.168.2.0` - Static IP Address
- `192.168.2.0/24` - CIDR Notation
- `*` - ALL Addresses
### IPv6
- `::1` - Static IP Address
- `::1/10` - CIDR Notation
- `*` - ALL Addresses
## Error handling
To customize the error, return a `Response` in the third argument.
```ts
app.use(
'*',
ipRestriction(
getConnInfo,
{
denyList: ['192.168.2.0/24'],
},
async (remote, c) => {
return c.text(`Blocking access from ${remote.addr}`, 403)
}
)
)
```
# JSX Renderer Middleware
JSX Renderer Middleware allows you to set up the layout when rendering JSX with the `c.render()` function, without the need for using `c.setRenderer()`. Additionally, it enables access to instances of Context within components through the use of `useRequestContext()`.
## Import
```ts
import { Hono } from 'hono'
import { jsxRenderer, useRequestContext } from 'hono/jsx-renderer'
```
## Usage
```jsx
const app = new Hono()
app.get(
'/page/*',
jsxRenderer(({ children }) => {
return (
Menu
)
})
```
## Options
### docType: `boolean` | `string`
If you do not want to add a DOCTYPE at the beginning of the HTML, set the `docType` option to `false`.
```tsx
app.use(
'*',
jsxRenderer(
({ children }) => {
return (
{children}
)
},
{ docType: false }
)
)
```
And you can specify the DOCTYPE.
```tsx
app.use(
'*',
jsxRenderer(
({ children }) => {
return (
{children}
)
},
{
docType:
'',
}
)
)
```
### stream: `boolean` | `Record`
If you set it to `true` or provide a Record value, it will be rendered as a streaming response.
```tsx
const AsyncComponent = async () => {
await new Promise((r) => setTimeout(r, 1000)) // sleep 1s
return
{children}
)
},
{ stream: true }
)
)
app.get('/', (c) => {
return c.render(
loading...}>
)
})
```
If `true` is set, the following headers are added:
```ts
{
'Transfer-Encoding': 'chunked',
'Content-Type': 'text/html; charset=UTF-8',
'Content-Encoding': 'Identity'
}
```
You can customize the header values by specifying the Record values.
## Nested Layouts
The `Layout` component enables nesting the layouts.
```tsx
app.use(
jsxRenderer(({ children }) => {
return (
{children}
)
})
)
const blog = new Hono()
blog.use(
jsxRenderer(({ children, Layout }) => {
return (
{children}
)
})
)
app.route('/blog', blog)
```
## `useRequestContext()`
`useRequestContext()` returns an instance of Context.
```tsx
import { useRequestContext, jsxRenderer } from 'hono/jsx-renderer'
const app = new Hono()
app.use(jsxRenderer())
const RequestUrlBadge: FC = () => {
const c = useRequestContext()
return {c.req.url}
}
app.get('/page/info', (c) => {
return c.render(
You are accessing:
)
})
```
::: warning
You can't use `useRequestContext()` with the Deno's `precompile` JSX option. Use the `react-jsx`:
```json
"compilerOptions": {
"jsx": "precompile", // [!code --]
"jsx": "react-jsx", // [!code ++]
"jsxImportSource": "hono/jsx"
}
}
```
:::
## Extending `ContextRenderer`
By defining `ContextRenderer` as shown below, you can pass additional content to the renderer. This is handy, for instance, when you want to change the contents of the head tag depending on the page.
```tsx
declare module 'hono' {
interface ContextRenderer {
(
content: string | Promise,
props: { title: string }
): Response
}
}
const app = new Hono()
app.get(
'/page/*',
jsxRenderer(({ children, title }) => {
return (
{title}Menu
,
{
title: 'My favorites',
}
)
})
```
# JWK Auth Middleware
The JWK Auth Middleware authenticates requests by verifying tokens using JWK (JSON Web Key). It checks for an `Authorization` header and other configured sources, such as cookies, if specified. Specifically, it validates tokens using the provided `keys`, retrieves keys from `jwks_uri` if specified, and supports token extraction from cookies if the `cookie` option is set.
:::info
The Authorization header sent from the client must have a specified scheme.
Example: `Bearer my.token.value` or `Basic my.token.value`
:::
## Import
```ts
import { Hono } from 'hono'
import { jwk } from 'hono/jwk'
```
## Usage
```ts
const app = new Hono()
app.use(
'/auth/*',
jwk({
jwks_uri: `https://${backendServer}/.well-known/jwks.json`,
})
)
app.get('/auth/page', (c) => {
return c.text('You are authorized')
})
```
Get payload:
```ts
const app = new Hono()
app.use(
'/auth/*',
jwk({
jwks_uri: `https://${backendServer}/.well-known/jwks.json`,
})
)
app.get('/auth/page', (c) => {
const payload = c.get('jwtPayload')
return c.json(payload) // eg: { "sub": "1234567890", "name": "John Doe", "iat": 1516239022 }
})
```
## Options
### keys: `HonoJsonWebKey[] | (() => Promise)`
The values of your public keys, or a function that returns them.
### jwks_uri: `string`
If this value is set, attempt to fetch JWKs from this URI, expecting a JSON response with `keys`, which are added to the provided `keys` option.
### cookie: `string`
If this value is set, then the value is retrieved from the cookie header using that value as a key, which is then validated as a token.
# JWT Auth Middleware
The JWT Auth Middleware provides authentication by verifying the token with JWT.
The middleware will check for an `Authorization` header if the `cookie` option is not set.
:::info
The Authorization header sent from the client must have a specified scheme.
Example: `Bearer my.token.value` or `Basic my.token.value`
:::
## Import
```ts
import { Hono } from 'hono'
import { jwt } from 'hono/jwt'
import type { JwtVariables } from 'hono/jwt'
```
## Usage
```ts
// Specify the variable types to infer the `c.get('jwtPayload')`:
type Variables = JwtVariables
const app = new Hono<{ Variables: Variables }>()
app.use(
'/auth/*',
jwt({
secret: 'it-is-very-secret',
})
)
app.get('/auth/page', (c) => {
return c.text('You are authorized')
})
```
Get payload:
```ts
const app = new Hono()
app.use(
'/auth/*',
jwt({
secret: 'it-is-very-secret',
})
)
app.get('/auth/page', (c) => {
const payload = c.get('jwtPayload')
return c.json(payload) // eg: { "sub": "1234567890", "name": "John Doe", "iat": 1516239022 }
})
```
::: tip
`jwt()` is just a middleware function. If you want to use an environment variable (eg: `c.env.JWT_SECRET`), you can use it as follows:
```js
app.use('/auth/*', (c, next) => {
const jwtMiddleware = jwt({
secret: c.env.JWT_SECRET,
})
return jwtMiddleware(c, next)
})
```
:::
## Options
### secret: `string`
A value of your secret key.
### cookie: `string`
If this value is set, then the value is retrieved from the cookie header using that value as a key, which is then validated as a token.
### alg: `string`
An algorithm type that is used for verifying.
The default is `HS256`.
Available types are `HS256` | `HS384` | `HS512` | `RS256` | `RS384` | `RS512` | `PS256` | `PS384` | `PS512` | `ES256` | `ES384` | `ES512` | `EdDSA`.
# Language Middleware
The Language Detector middleware automatically determines a user's preferred language (locale) from various sources and makes it available via `c.get('language')`. Detection strategies include query parameters, cookies, headers, and URL path segments. Perfect for internationalization (i18n) and locale-specific content.
## Import
```ts
import { Hono } from 'hono'
import { languageDetector } from 'hono/language'
```
## Basic Usage
Detect language from query string, cookie, and header (default order), with fallback to English:
```ts
const app = new Hono()
app.use(
languageDetector({
supportedLanguages: ['en', 'ar', 'ja'], // Must include fallback
fallbackLanguage: 'en', // Required
})
)
app.get('/', (c) => {
const lang = c.get('language')
return c.text(`Hello! Your language is ${lang}`)
})
```
### Client Examples
```sh
# Via path
curl http://localhost:8787/ar/home
# Via query parameter
curl http://localhost:8787/?lang=ar
# Via cookie
curl -H 'Cookie: language=ja' http://localhost:8787/
# Via header
curl -H 'Accept-Language: ar,en;q=0.9' http://localhost:8787/
```
## Default Configuration
```ts
export const DEFAULT_OPTIONS: DetectorOptions = {
order: ['querystring', 'cookie', 'header'],
lookupQueryString: 'lang',
lookupCookie: 'language',
lookupFromHeaderKey: 'accept-language',
lookupFromPathIndex: 0,
caches: ['cookie'],
ignoreCase: true,
fallbackLanguage: 'en',
supportedLanguages: ['en'],
cookieOptions: {
sameSite: 'Strict',
secure: true,
maxAge: 365 * 24 * 60 * 60,
httpOnly: true,
},
debug: false,
}
```
## Key Behaviors
### Detection Workflow
1. **Order**: Checks sources in this sequence by default:
- Query parameter (?lang=ar)
- Cookie (language=ar)
- Accept-Language header
2. **Caching**: Stores detected language in a cookie (1 year by default)
3. **Fallback**: Uses `fallbackLanguage` if no valid detection (must be in `supportedLanguages`)
## Advanced Configuration
### Custom Detection Order
Prioritize URL path detection (e.g., /en/about):
```ts
app.use(
languageDetector({
order: ['path', 'cookie', 'querystring', 'header'],
lookupFromPathIndex: 0, // /en/profile → index 0 = 'en'
supportedLanguages: ['en', 'ar'],
fallbackLanguage: 'en',
})
)
```
### Language Code Transformation
Normalize complex codes (e.g., en-US → en):
```ts
app.use(
languageDetector({
convertDetectedLanguage: (lang) => lang.split('-')[0],
supportedLanguages: ['en', 'ja'],
fallbackLanguage: 'en',
})
)
```
### Cookie Configuration
```ts
app.use(
languageDetector({
lookupCookie: 'app_lang',
caches: ['cookie'],
cookieOptions: {
path: '/', // Cookie path
sameSite: 'Lax', // Cookie same-site policy
secure: true, // Only send over HTTPS
maxAge: 86400 * 365, // 1 year expiration
httpOnly: true, // Not accessible via JavaScript
domain: '.example.com', // Optional: specific domain
},
})
)
```
To disable cookie caching:
```ts
languageDetector({
caches: false,
})
```
### Debugging
Log detection steps:
```ts
languageDetector({
debug: true, // Shows: "Detected from querystring: ar"
})
```
## Options Reference
### Basic Options
| Option | Type | Default | Required | Description |
| :------------------- | :--------------- | :------------------------------------ | :------- | :--------------------- |
| `supportedLanguages` | `string[]` | `['en']` | Yes | Allowed language codes |
| `fallbackLanguage` | `string` | `'en'` | Yes | Default language |
| `order` | `DetectorType[]` | `['querystring', 'cookie', 'header']` | No | Detection sequence |
| `debug` | `boolean` | `false` | No | Enable logging |
### Detection Options
| Option | Type | Default | Description |
| :-------------------- | :------- | :------------------ | :------------------- |
| `lookupQueryString` | `string` | `'lang'` | Query parameter name |
| `lookupCookie` | `string` | `'language'` | Cookie name |
| `lookupFromHeaderKey` | `string` | `'accept-language'` | Header name |
| `lookupFromPathIndex` | `number` | `0` | Path segment index |
### Cookie Options
| Option | Type | Default | Description |
| :----------------------- | :---------------------------- | :----------- | :------------------- |
| `caches` | `CacheType[] \| false` | `['cookie']` | Cache settings |
| `cookieOptions.path` | `string` | `'/'` | Cookie path |
| `cookieOptions.sameSite` | `'Strict' \| 'Lax' \| 'None'` | `'Strict'` | SameSite policy |
| `cookieOptions.secure` | `boolean` | `true` | HTTPS only |
| `cookieOptions.maxAge` | `number` | `31536000` | Expiration (seconds) |
| `cookieOptions.httpOnly` | `boolean` | `true` | JS accessibility |
| `cookieOptions.domain` | `string` | `undefined` | Cookie domain |
### Advanced Options
| Option | Type | Default | Description |
| :------------------------ | :------------------------- | :---------- | :------------------------ |
| `ignoreCase` | `boolean` | `true` | Case-insensitive matching |
| `convertDetectedLanguage` | `(lang: string) => string` | `undefined` | Language code transformer |
## Validation & Error Handling
- `fallbackLanguage` must be in `supportedLanguages` (throws error during setup)
- `lookupFromPathIndex` must be ≥ 0
- Invalid configurations throw errors during middleware initialization
- Failed detections silently use `fallbackLanguage`
## Common Recipes
### Path-Based Routing
```ts
app.get('/:lang/home', (c) => {
const lang = c.get('language') // 'en', 'ar', etc.
return c.json({ message: getLocalizedContent(lang) })
})
```
### Multiple Supported Languages
```ts
languageDetector({
supportedLanguages: ['en', 'en-GB', 'ar', 'ar-EG'],
convertDetectedLanguage: (lang) => lang.replace('_', '-'), // Normalize
})
```
# Logger Middleware
It's a simple logger.
## Import
```ts
import { Hono } from 'hono'
import { logger } from 'hono/logger'
```
## Usage
```ts
const app = new Hono()
app.use(logger())
app.get('/', (c) => c.text('Hello Hono!'))
```
## Logging Details
The Logger Middleware logs the following details for each request:
- **Incoming Request**: Logs the HTTP method, request path, and incoming request.
- **Outgoing Response**: Logs the HTTP method, request path, response status code, and request/response times.
- **Status Code Coloring**: Response status codes are color-coded for better visibility and quick identification of status categories. Different status code categories are represented by different colors.
- **Elapsed Time**: The time taken for the request/response cycle is logged in a human-readable format, either in milliseconds (ms) or seconds (s).
By using the Logger Middleware, you can easily monitor the flow of requests and responses in your Hono application and quickly identify any issues or performance bottlenecks.
You can also extend the middleware further by providing your own `PrintFunc` function for tailored logging behavior.
## PrintFunc
The Logger Middleware accepts an optional `PrintFunc` function as a parameter. This function allows you to customize the logger and add additional logs.
## Options
### fn: `PrintFunc(str: string, ...rest: string[])`
- `str`: Passed by the logger.
- `...rest`: Additional string props to be printed to console.
### Example
Setting up a custom `PrintFunc` function to the Logger Middleware:
```ts
export const customLogger = (message: string, ...rest: string[]) => {
console.log(message, ...rest)
}
app.use(logger(customLogger))
```
Setting up the custom logger in a route:
```ts
app.post('/blog', (c) => {
// Routing logic
customLogger('Blog saved:', `Path: ${blog.url},`, `ID: ${blog.id}`)
// Output
// <-- POST /blog
// Blog saved: Path: /blog/example, ID: 1
// --> POST /blog 201 93ms
// Return Context
})
```
# Method Override Middleware
This middleware executes the handler of the specified method, which is different from the actual method of the request, depending on the value of the form, header, or query, and returns its response.
## Import
```ts
import { Hono } from 'hono'
import { methodOverride } from 'hono/method-override'
```
## Usage
```ts
const app = new Hono()
// If no options are specified, the value of `_method` in the form,
// e.g. DELETE, is used as the method.
app.use('/posts', methodOverride({ app }))
app.delete('/posts', (c) => {
// ....
})
```
## For example
Since HTML forms cannot send a DELETE method, you can put the value `DELETE` in the property named `_method` and send it. And the handler for `app.delete()` will be executed.
The HTML form:
```html
```
The application:
```ts
import { methodOverride } from 'hono/method-override'
const app = new Hono()
app.use('/posts', methodOverride({ app }))
app.delete('/posts', () => {
// ...
})
```
You can change the default values or use the header value and query value:
```ts
app.use('/posts', methodOverride({ app, form: '_custom_name' }))
app.use(
'/posts',
methodOverride({ app, header: 'X-METHOD-OVERRIDE' })
)
app.use('/posts', methodOverride({ app, query: '_method' }))
```
## Options
### app: `Hono`
The instance of `Hono` is used in your application.
### form: `string`
Form key with a value containing the method name.
The default is `_method`.
### header: `boolean`
Header name with a value containing the method name.
### query: `boolean`
Query parameter key with a value containing the method name.
# Pretty JSON Middleware
Pretty JSON middleware enables "_JSON pretty print_" for JSON response body.
Adding `?pretty` to url query param, the JSON strings are prettified.
```js
// GET /
{"project":{"name":"Hono","repository":"https://github.com/honojs/hono"}}
```
will be:
```js
// GET /?pretty
{
"project": {
"name": "Hono",
"repository": "https://github.com/honojs/hono"
}
}
```
## Import
```ts
import { Hono } from 'hono'
import { prettyJSON } from 'hono/pretty-json'
```
## Usage
```ts
const app = new Hono()
app.use(prettyJSON()) // With options: prettyJSON({ space: 4 })
app.get('/', (c) => {
return c.json({ message: 'Hono!' })
})
```
## Options
### space: `number`
Number of spaces for indentation. The default is `2`.
### query: `string`
The name of the query string for applying. The default is `pretty`.
# Request ID Middleware
Request ID Middleware generates a unique ID for each request, which you can use in your handlers.
## Import
```ts
import { Hono } from 'hono'
import { requestId } from 'hono/request-id'
```
## Usage
You can access the Request ID through the `requestId` variable in the handlers and middleware to which the Request ID Middleware is applied.
```ts
const app = new Hono()
app.use('*', requestId())
app.get('/', (c) => {
return c.text(`Your request id is ${c.get('requestId')}`)
})
```
If you want to explicitly specify the type, import `RequestIdVariables` and pass it in the generics of `new Hono()`.
```ts
import type { RequestIdVariables } from 'hono/request-id'
const app = new Hono<{
Variables: RequestIdVariables
}>()
```
## Options
### limitLength: `number`
The maximum length of the request ID. The default is `255`.
### headerName: `string`
The header name used for the request ID. The default is `X-Request-Id`.
### generator: `(c: Context) => string`
The request ID generation function. By default, it uses `crypto.randomUUID()`.
# Secure Headers Middleware
Secure Headers Middleware simplifies the setup of security headers. Inspired in part by the capabilities of Helmet, it allows you to control the activation and deactivation of specific security headers.
## Import
```ts
import { Hono } from 'hono'
import { secureHeaders } from 'hono/secure-headers'
```
## Usage
You can use the optimal settings by default.
```ts
const app = new Hono()
app.use(secureHeaders())
```
You can suppress unnecessary headers by setting them to false.
```ts
const app = new Hono()
app.use(
'*',
secureHeaders({
xFrameOptions: false,
xXssProtection: false,
})
)
```
You can override default header values using a string.
```ts
const app = new Hono()
app.use(
'*',
secureHeaders({
strictTransportSecurity:
'max-age=63072000; includeSubDomains; preload',
xFrameOptions: 'DENY',
xXssProtection: '1',
})
)
```
## Supported Options
Each option corresponds to the following Header Key-Value pairs.
| Option | Header | Value | Default |
| ------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------ | -------------------------------------------------------------------------- | ---------- |
| - | X-Powered-By | (Delete Header) | True |
| contentSecurityPolicy | [Content-Security-Policy](https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP) | Usage: [Setting Content-Security-Policy](#setting-content-security-policy) | No Setting |
| contentSecurityPolicyReportOnly | [Content-Security-Policy-Report-Only](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy-Report-Only) | Usage: [Setting Content-Security-Policy](#setting-content-security-policy) | No Setting |
| crossOriginEmbedderPolicy | [Cross-Origin-Embedder-Policy](https://developer.mozilla.org/docs/Web/HTTP/Headers/Cross-Origin-Embedder-Policy) | require-corp | **False** |
| crossOriginResourcePolicy | [Cross-Origin-Resource-Policy](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cross-Origin-Resource-Policy) | same-origin | True |
| crossOriginOpenerPolicy | [Cross-Origin-Opener-Policy](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cross-Origin-Opener-Policy) | same-origin | True |
| originAgentCluster | [Origin-Agent-Cluster](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Origin-Agent-Cluster) | ?1 | True |
| referrerPolicy | [Referrer-Policy](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Referrer-Policy) | no-referrer | True |
| reportingEndpoints | [Reporting-Endpoints](https://www.w3.org/TR/reporting-1/#header) | Usage: [Setting Content-Security-Policy](#setting-content-security-policy) | No Setting |
| reportTo | [Report-To](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/report-to) | Usage: [Setting Content-Security-Policy](#setting-content-security-policy) | No Setting |
| strictTransportSecurity | [Strict-Transport-Security](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security) | max-age=15552000; includeSubDomains | True |
| xContentTypeOptions | [X-Content-Type-Options](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Content-Type-Options) | nosniff | True |
| xDnsPrefetchControl | [X-DNS-Prefetch-Control](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-DNS-Prefetch-Control) | off | True |
| xDownloadOptions | [X-Download-Options](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Download-Options) | noopen | True |
| xFrameOptions | [X-Frame-Options](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Frame-Options) | SAMEORIGIN | True |
| xPermittedCrossDomainPolicies | [X-Permitted-Cross-Domain-Policies](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Permitted-Cross-Domain-Policies) | none | True |
| xXssProtection | [X-XSS-Protection](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-XSS-Protection) | 0 | True |
| permissionPolicy | [Permissions-Policy](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Permissions-Policy) | Usage: [Setting Permission-Policy](#setting-permission-policy) | No Setting |
## Middleware Conflict
Please be cautious about the order of specification when dealing with middleware that manipulates the same header.
In this case, Secure-headers operates and the `x-powered-by` is removed:
```ts
const app = new Hono()
app.use(secureHeaders())
app.use(poweredBy())
```
In this case, Powered-By operates and the `x-powered-by` is added:
```ts
const app = new Hono()
app.use(poweredBy())
app.use(secureHeaders())
```
## Setting Content-Security-Policy
```ts
const app = new Hono()
app.use(
'/test',
secureHeaders({
reportingEndpoints: [
{
name: 'endpoint-1',
url: 'https://example.com/reports',
},
],
// -- or alternatively
// reportTo: [
// {
// group: 'endpoint-1',
// max_age: 10886400,
// endpoints: [{ url: 'https://example.com/reports' }],
// },
// ],
contentSecurityPolicy: {
defaultSrc: ["'self'"],
baseUri: ["'self'"],
childSrc: ["'self'"],
connectSrc: ["'self'"],
fontSrc: ["'self'", 'https:', 'data:'],
formAction: ["'self'"],
frameAncestors: ["'self'"],
frameSrc: ["'self'"],
imgSrc: ["'self'", 'data:'],
manifestSrc: ["'self'"],
mediaSrc: ["'self'"],
objectSrc: ["'none'"],
reportTo: 'endpoint-1',
sandbox: ['allow-same-origin', 'allow-scripts'],
scriptSrc: ["'self'"],
scriptSrcAttr: ["'none'"],
scriptSrcElem: ["'self'"],
styleSrc: ["'self'", 'https:', "'unsafe-inline'"],
styleSrcAttr: ['none'],
styleSrcElem: ["'self'", 'https:', "'unsafe-inline'"],
upgradeInsecureRequests: [],
workerSrc: ["'self'"],
},
})
)
```
### `nonce` attribute
You can add a [`nonce` attribute](https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/nonce) to a `script` or `style` element by adding the `NONCE` imported from `hono/secure-headers` to a `scriptSrc` or `styleSrc`:
```tsx
import { secureHeaders, NONCE } from 'hono/secure-headers'
import type { SecureHeadersVariables } from 'hono/secure-headers'
// Specify the variable types to infer the `c.get('secureHeadersNonce')`:
type Variables = SecureHeadersVariables
const app = new Hono<{ Variables: Variables }>()
// Set the pre-defined nonce value to `scriptSrc`:
app.get(
'*',
secureHeaders({
contentSecurityPolicy: {
scriptSrc: [NONCE, 'https://allowed1.example.com'],
},
})
)
// Get the value from `c.get('secureHeadersNonce')`:
app.get('/', (c) => {
return c.html(
{/** contents */}
)
})
```
If you want to generate the nonce value yourself, you can also specify a function as the following:
```tsx
const app = new Hono<{
Variables: { myNonce: string }
}>()
const myNonceGenerator: ContentSecurityPolicyOptionHandler = (c) => {
// This function is called on every request.
const nonce = Math.random().toString(36).slice(2)
c.set('myNonce', nonce)
return `'nonce-${nonce}'`
}
app.get(
'*',
secureHeaders({
contentSecurityPolicy: {
scriptSrc: [myNonceGenerator, 'https://allowed1.example.com'],
},
})
)
app.get('/', (c) => {
return c.html(
{/** contents */}
)
})
```
## Setting Permission-Policy
The Permission-Policy header allows you to control which features and APIs can be used in the browser. Here's an example of how to set it:
```ts
const app = new Hono()
app.use(
'*',
secureHeaders({
permissionsPolicy: {
fullscreen: ['self'], // fullscreen=(self)
bluetooth: ['none'], // bluetooth=(none)
payment: ['self', 'https://example.com'], // payment=(self "https://example.com")
syncXhr: [], // sync-xhr=()
camera: false, // camera=none
microphone: true, // microphone=*
geolocation: ['*'], // geolocation=*
usb: ['self', 'https://a.example.com', 'https://b.example.com'], // usb=(self "https://a.example.com" "https://b.example.com")
accelerometer: ['https://*.example.com'], // accelerometer=("https://*.example.com")
gyroscope: ['src'], // gyroscope=(src)
magnetometer: [
'https://a.example.com',
'https://b.example.com',
], // magnetometer=("https://a.example.com" "https://b.example.com")
},
})
)
```
# Timeout Middleware
The Timeout Middleware enables you to easily manage request timeouts in your application. It allows you to set a maximum duration for requests and optionally define custom error responses if the specified timeout is exceeded.
## Import
```ts
import { Hono } from 'hono'
import { timeout } from 'hono/timeout'
```
## Usage
Here's how to use the Timeout Middleware with both default and custom settings:
Default Settings:
```ts
const app = new Hono()
// Applying a 5-second timeout
app.use('/api', timeout(5000))
// Handling a route
app.get('/api/data', async (c) => {
// Your route handler logic
return c.json({ data: 'Your data here' })
})
```
Custom settings:
```ts
import { HTTPException } from 'hono/http-exception'
// Custom exception factory function
const customTimeoutException = (context) =>
new HTTPException(408, {
message: `Request timeout after waiting ${context.req.headers.get(
'Duration'
)} seconds. Please try again later.`,
})
// for Static Exception Message
// const customTimeoutException = new HTTPException(408, {
// message: 'Operation timed out. Please try again later.'
// });
// Applying a 1-minute timeout with a custom exception
app.use('/api/long-process', timeout(60000, customTimeoutException))
app.get('/api/long-process', async (c) => {
// Simulate a long process
await new Promise((resolve) => setTimeout(resolve, 61000))
return c.json({ data: 'This usually takes longer' })
})
```
## Notes
- The duration for the timeout can be specified in milliseconds. The middleware will automatically reject the promise and potentially throw an error if the specified duration is exceeded.
- The timeout middleware cannot be used with stream Thus, use `stream.close` and `setTimeout` together.
```ts
app.get('/sse', async (c) => {
let id = 0
let running = true
let timer: number | undefined
return streamSSE(c, async (stream) => {
timer = setTimeout(() => {
console.log('Stream timeout reached, closing stream')
stream.close()
}, 3000) as unknown as number
stream.onAbort(async () => {
console.log('Client closed connection')
running = false
clearTimeout(timer)
})
while (running) {
const message = `It is ${new Date().toISOString()}`
await stream.writeSSE({
data: message,
event: 'time-update',
id: String(id++),
})
await stream.sleep(1000)
}
})
})
```
## Middleware Conflicts
Be cautious about the order of middleware, especially when using error-handling or other timing-related middleware, as it might affect the behavior of this timeout middleware.
# Server-Timing Middleware
The [Server-Timing](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Server-Timing) Middleware provides
performance metrics in the response headers.
::: info
Note: On Cloudflare Workers, the timer metrics may not be accurate,
since [timers only show the time of last I/O](https://developers.cloudflare.com/workers/learning/security-model/#step-1-disallow-timers-and-multi-threading).
:::
## Import
```ts [npm]
import { Hono } from 'hono'
import { timing, setMetric, startTime, endTime } from 'hono/timing'
import type { TimingVariables } from 'hono/timing'
```
## Usage
```js
// Specify the variable types to infer the `c.get('metric')`:
type Variables = TimingVariables
const app = new Hono<{ Variables: Variables }>()
// add the middleware to your router
app.use(timing());
app.get('/', async (c) => {
// add custom metrics
setMetric(c, 'region', 'europe-west3')
// add custom metrics with timing, must be in milliseconds
setMetric(c, 'custom', 23.8, 'My custom Metric')
// start a new timer
startTime(c, 'db');
const data = await db.findMany(...);
// end the timer
endTime(c, 'db');
return c.json({ response: data });
});
```
### Conditionally enabled
```ts
const app = new Hono()
app.use(
'*',
timing({
// c: Context of the request
enabled: (c) => c.req.method === 'POST',
})
)
```
## Result
## Options
### total: `boolean`
Show the total response time. The default is `true`.
### enabled: `boolean` | `(c: Context) => boolean`
Whether timings should be added to the headers or not. The default is `true`.
### totalDescription: `boolean`
Description for the total response time. The default is `Total Response Time`.
### autoEnd: `boolean`
If `startTime()` should end automatically at the end of the request.
If disabled, not manually ended timers will not be shown.
### crossOrigin: `boolean` | `string` | `(c: Context) => boolean | string`
The origin this timings header should be readable.
- If false, only from current origin.
- If true, from all origin.
- If string, from this domain(s). Multiple domains must be separated with a comma.
The default is `false`. See more [docs](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Timing-Allow-Origin).
# Trailing Slash Middleware
This middleware handles Trailing Slash in the URL on a GET request.
`appendTrailingSlash` redirects the URL to which it added the Trailing Slash if the content was not found. Also, `trimTrailingSlash` will remove the Trailing Slash.
## Import
```ts
import { Hono } from 'hono'
import {
appendTrailingSlash,
trimTrailingSlash,
} from 'hono/trailing-slash'
```
## Usage
Example of redirecting a GET request of `/about/me` to `/about/me/`.
```ts
import { Hono } from 'hono'
import { appendTrailingSlash } from 'hono/trailing-slash'
const app = new Hono({ strict: true })
app.use(appendTrailingSlash())
app.get('/about/me/', (c) => c.text('With Trailing Slash'))
```
Example of redirecting a GET request of `/about/me/` to `/about/me`.
```ts
import { Hono } from 'hono'
import { trimTrailingSlash } from 'hono/trailing-slash'
const app = new Hono({ strict: true })
app.use(trimTrailingSlash())
app.get('/about/me', (c) => c.text('Without Trailing Slash'))
```
## Note
It will be enabled when the request method is `GET` and the response status is `404`.
# Accepts Helper
Accepts Helper helps to handle Accept headers in the Requests.
## Import
```ts
import { Hono } from 'hono'
import { accepts } from 'hono/accepts'
```
## `accepts()`
The `accepts()` function looks at the Accept header, such as Accept-Encoding and Accept-Language, and returns the proper value.
```ts
import { accepts } from 'hono/accepts'
app.get('/', (c) => {
const accept = accepts(c, {
header: 'Accept-Language',
supports: ['en', 'ja', 'zh'],
default: 'en',
})
return c.json({ lang: accept })
})
```
### `AcceptHeader` type
The definition of the `AcceptHeader` type is as follows.
```ts
export type AcceptHeader =
| 'Accept'
| 'Accept-Charset'
| 'Accept-Encoding'
| 'Accept-Language'
| 'Accept-Patch'
| 'Accept-Post'
| 'Accept-Ranges'
```
## Options
### header: `AcceptHeader`
The target accept header.
### supports: `string[]`
The header values which your application supports.
### default: `string`
The default values.
### match: `(accepts: Accept[], config: acceptsConfig) => string`
The custom match function.
# Adapter Helper
The Adapter Helper provides a seamless way to interact with various platforms through a unified interface.
## Import
```ts
import { Hono } from 'hono'
import { env, getRuntimeKey } from 'hono/adapter'
```
## `env()`
The `env()` function facilitates retrieving environment variables across different runtimes, extending beyond just Cloudflare Workers' Bindings. The value that can be retrieved with `env(c)` may be different for each runtimes.
```ts
import { env } from 'hono/adapter'
app.get('/env', (c) => {
// NAME is process.env.NAME on Node.js or Bun
// NAME is the value written in `wrangler.toml` on Cloudflare
const { NAME } = env<{ NAME: string }>(c)
return c.text(NAME)
})
```
Supported Runtimes, Serverless Platforms and Cloud Services:
- Cloudflare Workers
- `wrangler.toml`
- Deno
- [`Deno.env`](https://docs.deno.com/runtime/manual/basics/env_variables)
- `.env` file
- Bun
- [`Bun.env`](https://bun.sh/guides/runtime/set-env)
- `process.env`
- Node.js
- `process.env`
- Vercel
- [Environment Variables on Vercel](https://vercel.com/docs/projects/environment-variables)
- AWS Lambda
- [Environment Variables on AWS Lambda](https://docs.aws.amazon.com/lambda/latest/dg/samples-blank.html#samples-blank-architecture)
- Lambda@Edge\
Environment Variables on Lambda are [not supported](https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/add-origin-custom-headers.html) by Lambda@Edge, you need to use [Lamdba@Edge event](https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/lambda-event-structure.html) as an alternative.
- Fastly Compute\
On Fastly Compute, you can use the ConfigStore to manage user-defined data.
- Netlify\
On Netlify, you can use the [Netlify Contexts](https://docs.netlify.com/site-deploys/overview/#deploy-contexts) to manage user-defined data.
### Specify the runtime
You can specify the runtime to get environment variables by passing the runtime key as the second argument.
```ts
app.get('/env', (c) => {
const { NAME } = env<{ NAME: string }>(c, 'workerd')
return c.text(NAME)
})
```
## `getRuntimeKey()`
The `getRuntimeKey()` function returns the identifier of the current runtime.
```ts
app.get('/', (c) => {
if (getRuntimeKey() === 'workerd') {
return c.text('You are on Cloudflare')
} else if (getRuntimeKey() === 'bun') {
return c.text('You are on Bun')
}
...
})
```
### Available Runtimes Keys
Here are the available runtimes keys, unavailable runtime key runtimes may be supported and labeled as `other`, with some being inspired by [WinterCG's Runtime Keys](https://runtime-keys.proposal.wintercg.org/):
- `workerd` - Cloudflare Workers
- `deno`
- `bun`
- `node`
- `edge-light` - Vercel Edge Functions
- `fastly` - Fastly Compute
- `other` - Other unknown runtimes keys
# ConnInfo Helper
The ConnInfo Helper helps you to get the connection information. For example, you can get the client's remote address easily.
## Import
::: code-group
```ts [Cloudflare Workers]
import { Hono } from 'hono'
import { getConnInfo } from 'hono/cloudflare-workers'
```
```ts [Deno]
import { Hono } from 'hono'
import { getConnInfo } from 'hono/deno'
```
```ts [Bun]
import { Hono } from 'hono'
import { getConnInfo } from 'hono/bun'
```
```ts [Vercel]
import { Hono } from 'hono'
import { getConnInfo } from 'hono/vercel'
```
```ts [Lambda@Edge]
import { Hono } from 'hono'
import { getConnInfo } from 'hono/lambda-edge'
```
```ts [Node.js]
import { Hono } from 'hono'
import { getConnInfo } from '@hono/node-server/conninfo'
```
:::
## Usage
```ts
const app = new Hono()
app.get('/', (c) => {
const info = getConnInfo(c) // info is `ConnInfo`
return c.text(`Your remote address is ${info.remote.address}`)
})
```
## Type Definitions
The type definitions of the values that you can get from `getConnInfo()` are the following:
```ts
type AddressType = 'IPv6' | 'IPv4' | undefined
type NetAddrInfo = {
/**
* Transport protocol type
*/
transport?: 'tcp' | 'udp'
/**
* Transport port number
*/
port?: number
address?: string
addressType?: AddressType
} & (
| {
/**
* Host name such as IP Addr
*/
address: string
/**
* Host name type
*/
addressType: AddressType
}
| {}
)
/**
* HTTP Connection information
*/
interface ConnInfo {
/**
* Remote information
*/
remote: NetAddrInfo
}
```
# Cookie Helper
The Cookie Helper provides an easy interface to manage cookies, enabling developers to set, parse, and delete cookies seamlessly.
## Import
```ts
import { Hono } from 'hono'
import {
getCookie,
getSignedCookie,
setCookie,
setSignedCookie,
deleteCookie,
} from 'hono/cookie'
```
## Usage
**NOTE**: Setting and retrieving signed cookies returns a Promise due to the async nature of the WebCrypto API, which is used to create HMAC SHA-256 signatures.
```ts
const app = new Hono()
app.get('/cookie', (c) => {
const allCookies = getCookie(c)
const yummyCookie = getCookie(c, 'yummy_cookie')
// ...
setCookie(c, 'delicious_cookie', 'macha')
deleteCookie(c, 'delicious_cookie')
//
})
app.get('/signed-cookie', async (c) => {
const secret = 'secret ingredient'
// `getSignedCookie` will return `false` for a specified cookie if the signature was tampered with or is invalid
const allSignedCookies = await getSignedCookie(c, secret)
const fortuneCookie = await getSignedCookie(
c,
secret,
'fortune_cookie'
)
// ...
const anotherSecret = 'secret chocolate chips'
await setSignedCookie(c, 'great_cookie', 'blueberry', anotherSecret)
deleteCookie(c, 'great_cookie')
//
})
```
## Options
### `setCookie` & `setSignedCookie`
- domain: `string`
- expires: `Date`
- httpOnly: `boolean`
- maxAge: `number`
- path: `string`
- secure: `boolean`
- sameSite: `'Strict'` | `'Lax'` | `'None'`
- priority: `'Low' | 'Medium' | 'High'`
- prefix: `secure` | `'host'`
- partitioned: `boolean`
Example:
```ts
// Regular cookies
setCookie(c, 'great_cookie', 'banana', {
path: '/',
secure: true,
domain: 'example.com',
httpOnly: true,
maxAge: 1000,
expires: new Date(Date.UTC(2000, 11, 24, 10, 30, 59, 900)),
sameSite: 'Strict',
})
// Signed cookies
await setSignedCookie(
c,
'fortune_cookie',
'lots-of-money',
'secret ingredient',
{
path: '/',
secure: true,
domain: 'example.com',
httpOnly: true,
maxAge: 1000,
expires: new Date(Date.UTC(2000, 11, 24, 10, 30, 59, 900)),
sameSite: 'Strict',
}
)
```
### `deleteCookie`
- path: `string`
- secure: `boolean`
- domain: `string`
Example:
```ts
deleteCookie(c, 'banana', {
path: '/',
secure: true,
domain: 'example.com',
})
```
`deleteCookie` returns the deleted value:
```ts
const deletedCookie = deleteCookie(c, 'delicious_cookie')
```
## `__Secure-` and `__Host-` prefix
The Cookie helper supports `__Secure-` and `__Host-` prefix for cookies names.
If you want to verify if the cookie name has a prefix, specify the prefix option.
```ts
const securePrefixCookie = getCookie(c, 'yummy_cookie', 'secure')
const hostPrefixCookie = getCookie(c, 'yummy_cookie', 'host')
const securePrefixSignedCookie = await getSignedCookie(
c,
secret,
'fortune_cookie',
'secure'
)
const hostPrefixSignedCookie = await getSignedCookie(
c,
secret,
'fortune_cookie',
'host'
)
```
Also, if you wish to specify a prefix when setting the cookie, specify a value for the prefix option.
```ts
setCookie(c, 'delicious_cookie', 'macha', {
prefix: 'secure', // or `host`
})
await setSignedCookie(
c,
'delicious_cookie',
'macha',
'secret choco chips',
{
prefix: 'secure', // or `host`
}
)
```
## Following the best practices
A New Cookie RFC (a.k.a cookie-bis) and CHIPS include some best practices for Cookie settings that developers should follow.
- [RFC6265bis-13](https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-rfc6265bis-13)
- `Max-Age`/`Expires` limitation
- `__Host-`/`__Secure-` prefix limitation
- [CHIPS-01](https://www.ietf.org/archive/id/draft-cutler-httpbis-partitioned-cookies-01.html)
- `Partitioned` limitation
Hono is following the best practices.
The cookie helper will throw an `Error` when parsing cookies under the following conditions:
- The cookie name starts with `__Secure-`, but `secure` option is not set.
- The cookie name starts with `__Host-`, but `secure` option is not set.
- The cookie name starts with `__Host-`, but `path` is not `/`.
- The cookie name starts with `__Host-`, but `domain` is set.
- The `maxAge` option value is greater than 400 days.
- The `expires` option value is 400 days later than the current time.
# css Helper
The css helper - `hono/css` - is Hono's built-in CSS in JS(X).
You can write CSS in JSX in a JavaScript template literal named `css`. The return value of `css` will be the class name, which is set to the value of the class attribute. The `` component will then contain the value of the CSS.
## Import
```ts
import { Hono } from 'hono'
import { css, cx, keyframes, Style } from 'hono/css'
```
## `css`
You can write CSS in the `css` template literal. In this case, it uses `headerClass` as a value of the `class` attribute. Don't forget to add `` as it contains the CSS content.
```ts{10,13}
app.get('/', (c) => {
const headerClass = css`
background-color: orange;
color: white;
padding: 1rem;
`
return c.html(
Hello!
)
})
```
You can style pseudo-classes like `:hover` by using the [nesting selector](https://developer.mozilla.org/en-US/docs/Web/CSS/Nesting_selector), `&`:
```ts
const buttonClass = css`
background-color: #fff;
&:hover {
background-color: red;
}
`
```
### Extending
You can extend the CSS definition by embedding the class name.
```tsx
const baseClass = css`
color: white;
background-color: blue;
`
const header1Class = css`
${baseClass}
font-size: 3rem;
`
const header2Class = css`
${baseClass}
font-size: 2rem;
`
```
In addition, the syntax of `${baseClass} {}` enables nesting classes.
```tsx
const headerClass = css`
color: white;
background-color: blue;
`
const containerClass = css`
${headerClass} {
h1 {
font-size: 3rem;
}
}
`
return c.render(
Hello!
)
```
### Global styles
A pseudo-selector called `:-hono-global` allows you to define global styles.
```tsx
const globalClass = css`
:-hono-global {
html {
font-family: Arial, Helvetica, sans-serif;
}
}
`
return c.render(
Hello!
Today is a good day.
)
```
Or you can write CSS in the `` component with the `css` literal.
```tsx
export const renderer = jsxRenderer(({ children, title }) => {
return (
{title}
{children}
)
})
```
## `keyframes`
You can use `keyframes` to write the contents of `@keyframes`. In this case, `fadeInAnimation` will be the name of the animation
```tsx
const fadeInAnimation = keyframes`
from {
opacity: 0;
}
to {
opacity: 1;
}
`
const headerClass = css`
animation-name: ${fadeInAnimation};
animation-duration: 2s;
`
const Header = () => Hello!
```
## `cx`
The `cx` composites the two class names.
```tsx
const buttonClass = css`
border-radius: 10px;
`
const primaryClass = css`
background: orange;
`
const Button = () => (
Click!
)
```
It can also compose simple strings.
```tsx
const Header = () => Hi
```
## Usage in combination with [Secure Headers](/docs/middleware/builtin/secure-headers) middleware
If you want to use the css helpers in combination with the [Secure Headers](/docs/middleware/builtin/secure-headers) middleware, you can add the [`nonce` attribute](https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/nonce) to the `` to avoid Content-Security-Policy caused by the css helpers.
```tsx{8,23}
import { secureHeaders, NONCE } from 'hono/secure-headers'
app.get(
'*',
secureHeaders({
contentSecurityPolicy: {
// Set the pre-defined nonce value to `styleSrc`:
styleSrc: [NONCE],
},
})
)
app.get('/', (c) => {
const headerClass = css`
background-color: orange;
color: white;
padding: 1rem;
`
return c.html(
{/* Set the `nonce` attribute on the css helpers `style` and `script` elements */}
Hello!
)
})
```
## Tips
If you use VS Code, you can use [vscode-styled-components](https://marketplace.visualstudio.com/items?itemName=styled-components.vscode-styled-components) for Syntax highlighting and IntelliSense for css tagged literals.
# Dev Helper
Dev Helper provides useful methods you can use in development.
```ts
import { Hono } from 'hono'
import { getRouterName, showRoutes } from 'hono/dev'
```
## `getRouterName()`
You can get the name of the currently used router with `getRouterName()`.
```ts
const app = new Hono()
// ...
console.log(getRouterName(app))
```
## `showRoutes()`
`showRoutes()` function displays the registered routes in your console.
Consider an application like the following:
```ts
const app = new Hono().basePath('/v1')
app.get('/posts', (c) => {
// ...
})
app.get('/posts/:id', (c) => {
// ...
})
app.post('/posts', (c) => {
// ...
})
showRoutes(app, {
verbose: true,
})
```
When this application starts running, the routes will be shown in your console as follows:
```txt
GET /v1/posts
GET /v1/posts/:id
POST /v1/posts
```
## Options
### verbose: `boolean`
When set to `true`, it displays verbose information.
### colorize: `boolean`
When set to `false`, the output will not be colored.
# Factory Helper
The Factory Helper provides useful functions for creating Hono's components such as Middleware. Sometimes it's difficult to set the proper TypeScript types, but this helper facilitates that.
## Import
```ts
import { Hono } from 'hono'
import { createFactory, createMiddleware } from 'hono/factory'
```
## `createFactory()`
`createFactory()` will create an instance of the Factory class.
```ts
import { createFactory } from 'hono/factory'
const factory = createFactory()
```
You can pass your Env types as Generics:
```ts
type Env = {
Variables: {
foo: string
}
}
const factory = createFactory()
```
### Options
### defaultAppOptions: `HonoOptions`
The default options to pass to the Hono application created by `createApp()`.
```ts
const factory = createFactory({
defaultAppOptions: { strict: false },
})
const app = factory.createApp() // `strict: false` is applied
```
## `createMiddleware()`
`createMiddleware()` is shortcut of `factory.createMiddleware()`.
This function will create your custom middleware.
```ts
const messageMiddleware = createMiddleware(async (c, next) => {
await next()
c.res.headers.set('X-Message', 'Good morning!')
})
```
Tip: If you want to get an argument like `message`, you can create it as a function like the following.
```ts
const messageMiddleware = (message: string) => {
return createMiddleware(async (c, next) => {
await next()
c.res.headers.set('X-Message', message)
})
}
app.use(messageMiddleware('Good evening!'))
```
## `factory.createHandlers()`
`createHandlers()` helps to define handlers in a different place than `app.get('/')`.
```ts
import { createFactory } from 'hono/factory'
import { logger } from 'hono/logger'
// ...
const factory = createFactory()
const middleware = factory.createMiddleware(async (c, next) => {
c.set('foo', 'bar')
await next()
})
const handlers = factory.createHandlers(logger(), middleware, (c) => {
return c.json(c.var.foo)
})
app.get('/api', ...handlers)
```
## `factory.createApp()`
`createApp()` helps to create an instance of Hono with the proper types. If you use this method with `createFactory()`, you can avoid redundancy in the definition of the `Env` type.
If your application is like this, you have to set the `Env` in two places:
```ts
import { createMiddleware } from 'hono/factory'
type Env = {
Variables: {
myVar: string
}
}
// 1. Set the `Env` to `new Hono()`
const app = new Hono()
// 2. Set the `Env` to `createMiddleware()`
const mw = createMiddleware(async (c, next) => {
await next()
})
app.use(mw)
```
By using `createFactory()` and `createApp()`, you can set the `Env` only in one place.
```ts
import { createFactory } from 'hono/factory'
// ...
// Set the `Env` to `createFactory()`
const factory = createFactory()
const app = factory.createApp()
// factory also has `createMiddleware()`
const mw = factory.createMiddleware(async (c, next) => {
await next()
})
```
`createFactory()` can receive the `initApp` option to initialize an `app` created by `createApp()`. The following is an example that uses the option.
```ts
// factory-with-db.ts
type Env = {
Bindings: {
MY_DB: D1Database
}
Variables: {
db: DrizzleD1Database
}
}
export default createFactory({
initApp: (app) => {
app.use(async (c, next) => {
const db = drizzle(c.env.MY_DB)
c.set('db', db)
await next()
})
},
})
```
```ts
// crud.ts
import factoryWithDB from './factory-with-db'
const app = factoryWithDB.createApp()
app.post('/posts', (c) => {
c.var.db.insert()
// ...
})
```
# html Helper
The html Helper lets you write HTML in JavaScript template literal with a tag named `html`. Using `raw()`, the content will be rendered as is. You have to escape these strings by yourself.
## Import
```ts
import { Hono } from 'hono'
import { html, raw } from 'hono/html'
```
## `html`
```ts
const app = new Hono()
app.get('/:username', (c) => {
const { username } = c.req.param()
return c.html(
html`
Hello! ${username}!
`
)
})
```
### Insert snippets into JSX
Insert the inline script into JSX:
```tsx
app.get('/', (c) => {
return c.html(
Test Site
{html`
`}
Hello!
)
})
```
### Act as functional component
Since `html` returns an HtmlEscapedString, it can act as a fully functional component without using JSX.
#### Use `html` to speed up the process instead of `memo`
```typescript
const Footer = () => html`
`
```
### Receives props and embeds values
```typescript
interface SiteData {
title: string
description: string
image: string
children?: any
}
const Layout = (props: SiteData) => html`
${props.title}
${props.children}
`
const Content = (props: { siteData: SiteData; name: string }) => (
`)
})
```
## Tips
Thanks to these libraries, Visual Studio Code and vim also interprets template literals as HTML, allowing syntax highlighting and formatting to be applied.
-
-
# JWT Authentication Helper
This helper provides functions for encoding, decoding, signing, and verifying JSON Web Tokens (JWTs). JWTs are commonly used for authentication and authorization purposes in web applications. This helper offers robust JWT functionality with support for various cryptographic algorithms.
## Import
To use this helper, you can import it as follows:
```ts
import { decode, sign, verify } from 'hono/jwt'
```
::: info
[JWT Middleware](/docs/middleware/builtin/jwt) also import the `jwt` function from the `hono/jwt`.
:::
## `sign()`
This function generates a JWT token by encoding a payload and signing it using the specified algorithm and secret.
```ts
sign(
payload: unknown,
secret: string,
alg?: 'HS256';
): Promise;
```
### Example
```ts
import { sign } from 'hono/jwt'
const payload = {
sub: 'user123',
role: 'admin',
exp: Math.floor(Date.now() / 1000) + 60 * 5, // Token expires in 5 minutes
}
const secret = 'mySecretKey'
const token = await sign(payload, secret)
```
### Options
#### payload: `unknown`
The JWT payload to be signed. You can include other claims like in [Payload Validation](#payload-validation).
#### secret: `string`
The secret key used for JWT verification or signing.
#### alg: [AlgorithmTypes](#supported-algorithmtypes)
The algorithm used for JWT signing or verification. The default is HS256.
## `verify()`
This function checks if a JWT token is genuine and still valid. It ensures the token hasn't been altered and checks validity only if you added [Payload Validation](#payload-validation).
```ts
verify(
token: string,
secret: string,
alg?: 'HS256';
): Promise;
```
### Example
```ts
import { verify } from 'hono/jwt'
const tokenToVerify = 'token'
const secretKey = 'mySecretKey'
const decodedPayload = await verify(tokenToVerify, secretKey)
console.log(decodedPayload)
```
### Options
#### token: `string`
The JWT token to be verified.
#### secret: `string`
The secret key used for JWT verification or signing.
#### alg: [AlgorithmTypes](#supported-algorithmtypes)
The algorithm used for JWT signing or verification. The default is HS256.
## `decode()`
This function decodes a JWT token without performing signature verification. It extracts and returns the header and payload from the token.
```ts
decode(token: string): { header: any; payload: any };
```
### Example
```ts
import { decode } from 'hono/jwt'
// Decode the JWT token
const tokenToDecode =
'eyJhbGciOiAiSFMyNTYiLCAidHlwIjogIkpXVCJ9.eyJzdWIiOiAidXNlcjEyMyIsICJyb2xlIjogImFkbWluIn0.JxUwx6Ua1B0D1B0FtCrj72ok5cm1Pkmr_hL82sd7ELA'
const { header, payload } = decode(tokenToDecode)
console.log('Decoded Header:', header)
console.log('Decoded Payload:', payload)
```
### Options
#### token: `string`
The JWT token to be decoded.
> The `decode` function allows you to inspect the header and payload of a JWT token _**without**_ performing verification. This can be useful for debugging or extracting information from JWT tokens.
## Payload Validation
When verifying a JWT token, the following payload validations are performed:
- `exp`: The token is checked to ensure it has not expired.
- `nbf`: The token is checked to ensure it is not being used before a specified time.
- `iat`: The token is checked to ensure it is not issued in the future.
Please ensure that your JWT payload includes these fields, as an object, if you intend to perform these checks during verification.
## Custom Error Types
The module also defines custom error types to handle JWT-related errors.
- `JwtAlgorithmNotImplemented`: Indicates that the requested JWT algorithm is not implemented.
- `JwtTokenInvalid`: Indicates that the JWT token is invalid.
- `JwtTokenNotBefore`: Indicates that the token is being used before its valid date.
- `JwtTokenExpired`: Indicates that the token has expired.
- `JwtTokenIssuedAt`: Indicates that the "iat" claim in the token is incorrect.
- `JwtTokenSignatureMismatched`: Indicates a signature mismatch in the token.
## Supported AlgorithmTypes
The module supports the following JWT cryptographic algorithms:
- `HS256`: HMAC using SHA-256
- `HS384`: HMAC using SHA-384
- `HS512`: HMAC using SHA-512
- `RS256`: RSASSA-PKCS1-v1_5 using SHA-256
- `RS384`: RSASSA-PKCS1-v1_5 using SHA-384
- `RS512`: RSASSA-PKCS1-v1_5 using SHA-512
- `PS256`: RSASSA-PSS using SHA-256 and MGF1 with SHA-256
- `PS384`: RSASSA-PSS using SHA-386 and MGF1 with SHA-386
- `PS512`: RSASSA-PSS using SHA-512 and MGF1 with SHA-512
- `ES256`: ECDSA using P-256 and SHA-256
- `ES384`: ECDSA using P-384 and SHA-384
- `ES512`: ECDSA using P-521 and SHA-512
- `EdDSA`: EdDSA using Ed25519
# Proxy Helper
Proxy Helper provides useful functions when using Hono application as a (reverse) proxy.
## Import
```ts
import { Hono } from 'hono'
import { proxy } from 'hono/proxy'
```
## `proxy()`
`proxy()` is a `fetch()` API wrapper for proxy. The parameters and return value are the same as for `fetch()` (except for the proxy-specific options).
The `Accept-Encoding` header is replaced with an encoding that the current runtime can handle. Unnecessary response headers are deleted, and a `Response` object is returned that you can return as a response from the handler.
### Examples
Simple usage:
```ts
app.get('/proxy/:path', (c) => {
return proxy(`http://${originServer}/${c.req.param('path')}`)
})
```
Complicated usage:
```ts
app.get('/proxy/:path', async (c) => {
const res = await proxy(
`http://${originServer}/${c.req.param('path')}`,
{
headers: {
...c.req.header(), // optional, specify only when forwarding all the request data (including credentials) is necessary.
'X-Forwarded-For': '127.0.0.1',
'X-Forwarded-Host': c.req.header('host'),
Authorization: undefined, // do not propagate request headers contained in c.req.header('Authorization')
},
}
)
res.headers.delete('Set-Cookie')
return res
})
```
Or you can pass the `c.req` as a parameter.
```ts
app.all('/proxy/:path', (c) => {
return proxy(`http://${originServer}/${c.req.param('path')}`, {
...c.req, // optional, specify only when forwarding all the request data (including credentials) is necessary.
headers: {
...c.req.header(),
'X-Forwarded-For': '127.0.0.1',
'X-Forwarded-Host': c.req.header('host'),
Authorization: undefined, // do not propagate request headers contained in c.req.header('Authorization')
},
})
})
```
### `ProxyFetch`
The type of `proxy()` is defined as `ProxyFetch` and is as follows
```ts
interface ProxyRequestInit extends Omit {
raw?: Request
headers?:
| HeadersInit
| [string, string][]
| Record
| Record
}
interface ProxyFetch {
(
input: string | URL | Request,
init?: ProxyRequestInit
): Promise
}
```
# SSG Helper
SSG Helper generates a static site from your Hono application. It will retrieve the contents of registered routes and save them as static files.
## Usage
### Manual
If you have a simple Hono application like the following:
```tsx
// index.tsx
const app = new Hono()
app.get('/', (c) => c.html('Hello, World!'))
app.use('/about', async (c, next) => {
c.setRenderer((content, head) => {
return c.html(
{head.title ?? ''}
{content}
)
})
await next()
})
app.get('/about', (c) => {
return c.render('Hello!', { title: 'Hono SSG Page' })
})
export default app
```
For Node.js, create a build script like this:
```ts
// build.ts
import app from './index'
import { toSSG } from 'hono/ssg'
import fs from 'fs/promises'
toSSG(app, fs)
```
By executing the script, the files will be output as follows:
```bash
ls ./static
about.html index.html
```
### Vite Plugin
Using the `@hono/vite-ssg` Vite Plugin, you can easily handle the process.
For more details, see here:
https://github.com/honojs/vite-plugins/tree/main/packages/ssg
## toSSG
`toSSG` is the main function for generating static sites, taking an application and a filesystem module as arguments. It is based on the following:
### Input
The arguments for toSSG are specified in ToSSGInterface.
```ts
export interface ToSSGInterface {
(
app: Hono,
fsModule: FileSystemModule,
options?: ToSSGOptions
): Promise
}
```
- `app` specifies `new Hono()` with registered routes.
- `fs` specifies the following object, assuming `node:fs/promise`.
```ts
export interface FileSystemModule {
writeFile(path: string, data: string | Uint8Array): Promise
mkdir(
path: string,
options: { recursive: boolean }
): Promise
}
```
### Using adapters for Deno and Bun
If you want to use SSG on Deno or Bun, a `toSSG` function is provided for each file system.
For Deno:
```ts
import { toSSG } from 'hono/deno'
toSSG(app) // The second argument is an option typed `ToSSGOptions`.
```
For Bun:
```ts
import { toSSG } from 'hono/bun'
toSSG(app) // The second argument is an option typed `ToSSGOptions`.
```
### Options
Options are specified in the ToSSGOptions interface.
```ts
export interface ToSSGOptions {
dir?: string
concurrency?: number
beforeRequestHook?: BeforeRequestHook
afterResponseHook?: AfterResponseHook
afterGenerateHook?: AfterGenerateHook
extensionMap?: Record
}
```
- `dir` is the output destination for Static files. The default value is `./static`.
- `concurrency` is the concurrent number of files to be generated at the same time. The default value is `2`.
- `extensionMap` is a map containing the `Content-Type` as a key and the string of the extension as a value. This is used to determine the file extension of the output file.
Each Hook will be described later.
### Output
`toSSG` returns the result in the following Result type.
```ts
export interface ToSSGResult {
success: boolean
files: string[]
error?: Error
}
```
## Hook
You can customize the process of `toSSG` by specifying the following custom hooks in options.
```ts
export type BeforeRequestHook = (req: Request) => Request | false
export type AfterResponseHook = (res: Response) => Response | false
export type AfterGenerateHook = (
result: ToSSGResult
) => void | Promise
```
### BeforeRequestHook/AfterResponseHook
`toSSG` targets all routes registered in app, but if there are routes you want to exclude, you can filter them by specifying a Hook.
For example, if you want to output only GET requests, filter `req.method` in `beforeRequestHook`.
```ts
toSSG(app, fs, {
beforeRequestHook: (req) => {
if (req.method === 'GET') {
return req
}
return false
},
})
```
For example, if you want to output only when StatusCode is 200 or 500, filter `res.status` in `afterResponseHook`.
```ts
toSSG(app, fs, {
afterResponseHook: (res) => {
if (res.status === 200 || res.status === 500) {
return res
}
return false
},
})
```
### AfterGenerateHook
Use `afterGenerateHook` if you want to hook the result of `toSSG`.
```ts
toSSG(app, fs, {
afterGenerateHook: (result) => {
if (result.files) {
result.files.forEach((file) => console.log(file))
}
})
})
```
## Generate File
### Route and Filename
The following rules apply to the registered route information and the generated file name. The default `./static` behaves as follows:
- `/` -> `./static/index.html`
- `/path` -> `./static/path.html`
- `/path/` -> `./static/path/index.html`
### File Extension
The file extension depends on the `Content-Type` returned by each route. For example, responses from `c.html` are saved as `.html`.
If you want to customize the file extensions, set the `extensionMap` option.
```ts
import { toSSG, defaultExtensionMap } from 'hono/ssg'
// Save `application/x-html` content with `.html`
toSSG(app, fs, {
extensionMap: {
'application/x-html': 'html',
...defaultExtensionMap,
},
})
```
Note that paths ending with a slash are saved as index.ext regardless of the extension.
```ts
// save to ./static/html/index.html
app.get('/html/', (c) => c.html('html'))
// save to ./static/text/index.txt
app.get('/text/', (c) => c.text('text'))
```
## Middleware
Introducing built-in middleware that supports SSG.
### ssgParams
You can use an API like `generateStaticParams` of Next.js.
Example:
```ts
app.get(
'/shops/:id',
ssgParams(async () => {
const shops = await getShops()
return shops.map((shop) => ({ id: shop.id }))
}),
async (c) => {
const shop = await getShop(c.req.param('id'))
if (!shop) {
return c.notFound()
}
return c.render(
{shop.name}
)
}
)
```
### disableSSG
Routes with the `disableSSG` middleware set are excluded from static file generation by `toSSG`.
```ts
app.get('/api', disableSSG(), (c) => c.text('an-api'))
```
### onlySSG
Routes with the `onlySSG` middleware set will be overridden by `c.notFound()` after `toSSG` execution.
```ts
app.get('/static-page', onlySSG(), (c) => c.html(
Welcome to my site
))
```
# Streaming Helper
The Streaming Helper provides methods for streaming responses.
## Import
```ts
import { Hono } from 'hono'
import { stream, streamText, streamSSE } from 'hono/streaming'
```
## `stream()`
It returns a simple streaming response as `Response` object.
```ts
app.get('/stream', (c) => {
return stream(c, async (stream) => {
// Write a process to be executed when aborted.
stream.onAbort(() => {
console.log('Aborted!')
})
// Write a Uint8Array.
await stream.write(new Uint8Array([0x48, 0x65, 0x6c, 0x6c, 0x6f]))
// Pipe a readable stream.
await stream.pipe(anotherReadableStream)
})
})
```
## `streamText()`
It returns a streaming response with `Content-Type:text/plain`, `Transfer-Encoding:chunked`, and `X-Content-Type-Options:nosniff` headers.
```ts
app.get('/streamText', (c) => {
return streamText(c, async (stream) => {
// Write a text with a new line ('\n').
await stream.writeln('Hello')
// Wait 1 second.
await stream.sleep(1000)
// Write a text without a new line.
await stream.write(`Hono!`)
})
})
```
::: warning
If you are developing an application for Cloudflare Workers, a streaming may not work well on Wrangler. If so, add `Identity` for `Content-Encoding` header.
```ts
app.get('/streamText', (c) => {
c.header('Content-Encoding', 'Identity')
return streamText(c, async (stream) => {
// ...
})
})
```
:::
## `streamSSE()`
It allows you to stream Server-Sent Events (SSE) seamlessly.
```ts
const app = new Hono()
let id = 0
app.get('/sse', async (c) => {
return streamSSE(c, async (stream) => {
while (true) {
const message = `It is ${new Date().toISOString()}`
await stream.writeSSE({
data: message,
event: 'time-update',
id: String(id++),
})
await stream.sleep(1000)
}
})
})
```
## Error Handling
The third argument of the streaming helper is an error handler.
This argument is optional, if you don't specify it, the error will be output as a console error.
```ts
app.get('/stream', (c) => {
return stream(
c,
async (stream) => {
// Write a process to be executed when aborted.
stream.onAbort(() => {
console.log('Aborted!')
})
// Write a Uint8Array.
await stream.write(
new Uint8Array([0x48, 0x65, 0x6c, 0x6c, 0x6f])
)
// Pipe a readable stream.
await stream.pipe(anotherReadableStream)
},
(err, stream) => {
stream.writeln('An error occurred!')
console.error(err)
}
)
})
```
The stream will be automatically closed after the callbacks are executed.
::: warning
If the callback function of the streaming helper throws an error, the `onError` event of Hono will not be triggered.
`onError` is a hook to handle errors before the response is sent and overwrite the response. However, when the callback function is executed, the stream has already started, so it cannot be overwritten.
:::
# Testing Helper
The Testing Helper provides functions to make testing of Hono applications easier.
## Import
```ts
import { Hono } from 'hono'
import { testClient } from 'hono/testing'
```
## `testClient()`
The `testClient()` takes an instance of Hono as its first argument and returns an object of the [Hono Client](/docs/guides/rpc#client). By using this, you can define your request with the editor completion.
```ts
import { testClient } from 'hono/testing'
it('test', async () => {
const app = new Hono().get('/search', (c) =>
c.json({ hello: 'world' })
)
const res = await testClient(app).search.$get()
expect(await res.json()).toEqual({ hello: 'world' })
})
```
# WebSocket Helper
WebSocket Helper is a helper for server-side WebSockets in Hono applications.
Currently Cloudflare Workers / Pages, Deno, and Bun adapters are available.
## Import
::: code-group
```ts [Cloudflare Workers]
import { Hono } from 'hono'
import { upgradeWebSocket } from 'hono/cloudflare-workers'
```
```ts [Deno]
import { Hono } from 'hono'
import { upgradeWebSocket } from 'hono/deno'
```
```ts [Bun]
import { Hono } from 'hono'
import { createBunWebSocket } from 'hono/bun'
import type { ServerWebSocket } from 'bun'
const { upgradeWebSocket, websocket } =
createBunWebSocket()
// ...
export default {
fetch: app.fetch,
websocket,
}
```
:::
If you use Node.js, you can use [@hono/node-ws](https://github.com/honojs/middleware/tree/main/packages/node-ws).
## `upgradeWebSocket()`
`upgradeWebSocket()` returns a handler for handling WebSocket.
```ts
const app = new Hono()
app.get(
'/ws',
upgradeWebSocket((c) => {
return {
onMessage(event, ws) {
console.log(`Message from client: ${event.data}`)
ws.send('Hello from server!')
},
onClose: () => {
console.log('Connection closed')
},
}
})
)
```
Available events:
- `onOpen` - Currently, Cloudflare Workers does not support it.
- `onMessage`
- `onClose`
- `onError`
::: warning
If you use middleware that modifies headers (e.g., applying CORS) on a route that uses WebSocket Helper, you may encounter an error saying you can't modify immutable headers. This is because `upgradeWebSocket()` also changes headers internally.
Therefore, please be cautious if you are using WebSocket Helper and middleware at the same time.
:::
## RPC-mode
Handlers defined with WebSocket Helper support RPC mode.
```ts
// server.ts
const wsApp = app.get(
'/ws',
upgradeWebSocket((c) => {
//...
})
)
export type WebSocketApp = typeof wsApp
// client.ts
const client = hc('http://localhost:8787')
const socket = client.ws.$ws() // A WebSocket object for a client
```
## Examples
See the examples using WebSocket Helper.
### Server and Client
```ts
// server.ts
import { Hono } from 'hono'
import { upgradeWebSocket } from 'hono/cloudflare-workers'
const app = new Hono().get(
'/ws',
upgradeWebSocket(() => {
return {
onMessage: (event) => {
console.log(event.data)
},
}
})
)
export default app
```
```ts
// client.ts
import { hc } from 'hono/client'
import type app from './server'
const client = hc('http://localhost:8787')
const ws = client.ws.$ws(0)
ws.addEventListener('open', () => {
setInterval(() => {
ws.send(new Date().toString())
}, 1000)
})
```
### Bun with JSX
```tsx
import { Hono } from 'hono'
import { createBunWebSocket } from 'hono/bun'
const { upgradeWebSocket, websocket } = createBunWebSocket()
const app = new Hono()
app.get('/', (c) => {
return c.html(
)
})
const ws = app.get(
'/ws',
upgradeWebSocket((c) => {
let intervalId
return {
onOpen(_event, ws) {
intervalId = setInterval(() => {
ws.send(new Date().toString())
}, 200)
},
onClose() {
clearInterval(intervalId)
},
}
})
)
export default {
fetch: app.fetch,
websocket,
}
```
# Best Practices
Hono is very flexible. You can write your app as you like.
However, there are best practices that are better to follow.
## Don't make "Controllers" when possible
When possible, you should not create "Ruby on Rails-like Controllers".
```ts
// 🙁
// A RoR-like Controller
const booksList = (c: Context) => {
return c.json('list books')
}
app.get('/books', booksList)
```
The issue is related to types. For example, the path parameter cannot be inferred in the Controller without writing complex generics.
```ts
// 🙁
// A RoR-like Controller
const bookPermalink = (c: Context) => {
const id = c.req.param('id') // Can't infer the path param
return c.json(`get ${id}`)
}
```
Therefore, you don't need to create RoR-like controllers and should write handlers directly after path definitions.
```ts
// 😃
app.get('/books/:id', (c) => {
const id = c.req.param('id') // Can infer the path param
return c.json(`get ${id}`)
})
```
## `factory.createHandlers()` in `hono/factory`
If you still want to create a RoR-like Controller, use `factory.createHandlers()` in [`hono/factory`](/docs/helpers/factory). If you use this, type inference will work correctly.
```ts
import { createFactory } from 'hono/factory'
import { logger } from 'hono/logger'
// ...
// 😃
const factory = createFactory()
const middleware = factory.createMiddleware(async (c, next) => {
c.set('foo', 'bar')
await next()
})
const handlers = factory.createHandlers(logger(), middleware, (c) => {
return c.json(c.var.foo)
})
app.get('/api', ...handlers)
```
## Building a larger application
Use `app.route()` to build a larger application without creating "Ruby on Rails-like Controllers".
If your application has `/authors` and `/books` endpoints and you wish to separate files from `index.ts`, create `authors.ts` and `books.ts`.
```ts
// authors.ts
import { Hono } from 'hono'
const app = new Hono()
app.get('/', (c) => c.json('list authors'))
app.post('/', (c) => c.json('create an author', 201))
app.get('/:id', (c) => c.json(`get ${c.req.param('id')}`))
export default app
```
```ts
// books.ts
import { Hono } from 'hono'
const app = new Hono()
app.get('/', (c) => c.json('list books'))
app.post('/', (c) => c.json('create a book', 201))
app.get('/:id', (c) => c.json(`get ${c.req.param('id')}`))
export default app
```
Then, import them and mount on the paths `/authors` and `/books` with `app.route()`.
```ts
// index.ts
import { Hono } from 'hono'
import authors from './authors'
import books from './books'
const app = new Hono()
// 😃
app.route('/authors', authors)
app.route('/books', books)
export default app
```
### If you want to use RPC features
The code above works well for normal use cases.
However, if you want to use the `RPC` feature, you can get the correct type by chaining as follows.
```ts
// authors.ts
import { Hono } from 'hono'
const app = new Hono()
.get('/', (c) => c.json('list authors'))
.post('/', (c) => c.json('create an author', 201))
.get('/:id', (c) => c.json(`get ${c.req.param('id')}`))
export default app
```
If you pass the type of the `app` to `hc`, it will get the correct type.
```ts
import app from './authors'
import { hc } from 'hono/client'
// 😃
const client = hc('http://localhost') // Typed correctly
```
For more detailed information, please see [the RPC page](/docs/guides/rpc#using-rpc-with-larger-applications).
# Examples
See the [Examples section](/examples/).
# Frequently Asked Questions
This guide is a collection of frequently asked questions (FAQ) about Hono and how to resolve them.
## Is there an official Renovate config for Hono?
The Hono teams does not currently maintain [Renovate](https://github.com/renovatebot/renovate) Configuration.
Therefore, please use third-party renovate-config as follows.
In your `renovate.json` :
```json
// renovate.json
{
"$schema": "https://docs.renovatebot.com/renovate-schema.json",
"extends": [
"github>shinGangan/renovate-config-hono" // [!code ++]
]
}
```
see [renovate-config-hono](https://github.com/shinGangan/renovate-config-hono) repository for more details.
# Helpers
Helpers are available to assist in developing your application. Unlike middleware, they don't act as handlers, but rather provide useful functions.
For instance, here's how to use the [Cookie helper](/docs/helpers/cookie):
```ts
import { getCookie, setCookie } from 'hono/cookie'
const app = new Hono()
app.get('/cookie', (c) => {
const yummyCookie = getCookie(c, 'yummy_cookie')
// ...
setCookie(c, 'delicious_cookie', 'macha')
//
})
```
## Available Helpers
- [Accepts](/docs/helpers/accepts)
- [Adapter](/docs/helpers/adapter)
- [Cookie](/docs/helpers/cookie)
- [css](/docs/helpers/css)
- [Dev](/docs/helpers/dev)
- [Factory](/docs/helpers/factory)
- [html](/docs/helpers/html)
- [JWT](/docs/helpers/jwt)
- [SSG](/docs/helpers/ssg)
- [Streaming](/docs/helpers/streaming)
- [Testing](/docs/helpers/testing)
- [WebSocket](/docs/helpers/websocket)
# Client Components
`hono/jsx` supports not only server side but also client side. This means that it is possible to create an interactive UI that runs in the browser. We call it Client Components or `hono/jsx/dom`.
It is fast and very small. The counter program in `hono/jsx/dom` is only 2.8KB with Brotli compression. But, 47.8KB for React.
This section introduces Client Components-specific features.
## Counter example
Here is an example of a simple counter, the same code works as in React.
```tsx
import { useState } from 'hono/jsx'
import { render } from 'hono/jsx/dom'
function Counter() {
const [count, setCount] = useState(0)
return (
Count: {count}
)
}
function App() {
return (
)
}
const root = document.getElementById('root')
render(, root)
```
## `render()`
You can use `render()` to insert JSX components within a specified HTML element.
```tsx
render(, container)
```
## Hooks compatible with React
hono/jsx/dom has Hooks that are compatible or partially compatible with React. You can learn about these APIs by looking at [the React documentation](https://react.dev/reference/react/hooks).
- `useState()`
- `useEffect()`
- `useRef()`
- `useCallback()`
- `use()`
- `startTransition()`
- `useTransition()`
- `useDeferredValue()`
- `useMemo()`
- `useLayoutEffect()`
- `useReducer()`
- `useDebugValue()`
- `createElement()`
- `memo()`
- `isValidElement()`
- `useId()`
- `createRef()`
- `forwardRef()`
- `useImperativeHandle()`
- `useSyncExternalStore()`
- `useInsertionEffect()`
- `useFormStatus()`
- `useActionState()`
- `useOptimistic()`
## `startViewTransition()` family
The `startViewTransition()` family contains original hooks and functions to handle [View Transitions API](https://developer.mozilla.org/en-US/docs/Web/API/View_Transitions_API) easily. The followings are examples of how to use them.
### 1. An easiest example
You can write a transition using the `document.startViewTransition` shortly with the `startViewTransition()`.
```tsx
import { useState, startViewTransition } from 'hono/jsx'
import { css, Style } from 'hono/css'
export default function App() {
const [showLargeImage, setShowLargeImage] = useState(false)
return (
<>
{!showLargeImage ? (
) : (
)}
)
}
```
### 2. Using `viewTransition()` with `keyframes()`
The `viewTransition()` function allows you to get the unique `view-transition-name`.
You can use it with the `keyframes()`, The `::view-transition-old()` is converted to `::view-transition-old(${uniqueName))`.
```tsx
import { useState, startViewTransition } from 'hono/jsx'
import { viewTransition } from 'hono/jsx/dom/css'
import { css, keyframes, Style } from 'hono/css'
const rotate = keyframes`
from {
rotate: 0deg;
}
to {
rotate: 360deg;
}
`
export default function App() {
const [showLargeImage, setShowLargeImage] = useState(false)
const [transitionNameClass] = useState(() =>
viewTransition(css`
::view-transition-old() {
animation-name: ${rotate};
}
::view-transition-new() {
animation-name: ${rotate};
}
`)
)
return (
<>
{!showLargeImage ? (
) : (
)}
)
}
```
### 3. Using `useViewTransition`
If you want to change the style only during the animation. You can use `useViewTransition()`. This hook returns the `[boolean, (callback: () => void) => void]`, and they are the `isUpdating` flag and the `startViewTransition()` function.
When this hook is used, the Component is evaluated at the following two times.
- Inside the callback of a call to `startViewTransition()`.
- When [the `finish` promise becomes fulfilled](https://developer.mozilla.org/en-US/docs/Web/API/ViewTransition/finished)
```tsx
import { useState, useViewTransition } from 'hono/jsx'
import { viewTransition } from 'hono/jsx/dom/css'
import { css, keyframes, Style } from 'hono/css'
const rotate = keyframes`
from {
rotate: 0deg;
}
to {
rotate: 360deg;
}
`
export default function App() {
const [isUpdating, startViewTransition] = useViewTransition()
const [showLargeImage, setShowLargeImage] = useState(false)
const [transitionNameClass] = useState(() =>
viewTransition(css`
::view-transition-old() {
animation-name: ${rotate};
}
::view-transition-new() {
animation-name: ${rotate};
}
`)
)
return (
<>
{!showLargeImage ? (
) : (
)}
)
}
```
## The `hono/jsx/dom` runtime
There is a small JSX Runtime for Client Components. Using this will result in smaller bundled results than using `hono/jsx`. Specify `hono/jsx/dom` in `tsconfig.json`. For Deno, modify the deno.json.
```json
{
"compilerOptions": {
"jsx": "react-jsx",
"jsxImportSource": "hono/jsx/dom"
}
}
```
# JSX
You can write HTML with JSX syntax with `hono/jsx`.
Although `hono/jsx` works on the client, you will probably use it most often when rendering content on the server side. Here are some things related to JSX that are common to both server and client.
## Settings
To use JSX, modify the `tsconfig.json`:
`tsconfig.json`:
```json
{
"compilerOptions": {
"jsx": "react-jsx",
"jsxImportSource": "hono/jsx"
}
}
```
Alternatively, use the pragma directives:
```ts
/** @jsx jsx */
/** @jsxImportSource hono/jsx */
```
For Deno, you have to modify the `deno.json` instead of the `tsconfig.json`:
```json
{
"compilerOptions": {
"jsx": "precompile",
"jsxImportSource": "hono/jsx"
}
}
```
## Usage
`index.tsx`:
```tsx
import { Hono } from 'hono'
import type { FC } from 'hono/jsx'
const app = new Hono()
const Layout: FC = (props) => {
return (
{props.children}
)
}
const Top: FC<{ messages: string[] }> = (props: {
messages: string[]
}) => {
return (
Hello Hono!
{props.messages.map((message) => {
return
{message}!!
})}
)
}
app.get('/', (c) => {
const messages = ['Good Morning', 'Good Evening', 'Good Night']
return c.html()
})
export default app
```
## Fragment
Use Fragment to group multiple elements without adding extra nodes:
```tsx
import { Fragment } from 'hono/jsx'
const List = () => (
first child
second child
third child
)
```
Or you can write it with `<>` if it set up properly.
```tsx
const List = () => (
<>
first child
second child
third child
)
```
## `PropsWithChildren`
You can use `PropsWithChildren` to correctly infer a child element in a function component.
```tsx
import { PropsWithChildren } from 'hono/jsx'
type Post = {
id: number
title: string
}
function Component({ title, children }: PropsWithChildren) {
return (
{title}
{children}
)
}
```
## Inserting Raw HTML
To directly insert HTML, use `dangerouslySetInnerHTML`:
```tsx
app.get('/foo', (c) => {
const inner = { __html: 'JSX · SSR' }
const Div =
})
```
## Memoization
Optimize your components by memoizing computed strings using `memo`:
```tsx
import { memo } from 'hono/jsx'
const Header = memo(() => Welcome to Hono)
const Footer = memo(() => )
const Layout = (
Hono is cool!
)
```
## Context
By using `useContext`, you can share data globally across any level of the Component tree without passing values through props.
```tsx
import type { FC } from 'hono/jsx'
import { createContext, useContext } from 'hono/jsx'
const themes = {
light: {
color: '#000000',
background: '#eeeeee',
},
dark: {
color: '#ffffff',
background: '#222222',
},
}
const ThemeContext = createContext(themes.light)
const Button: FC = () => {
const theme = useContext(ThemeContext)
return
}
const Toolbar: FC = () => {
return (
)
}
// ...
app.get('/', (c) => {
return c.html(
)
})
```
## Async Component
`hono/jsx` supports an Async Component, so you can use `async`/`await` in your component.
If you render it with `c.html()`, it will await automatically.
```tsx
const AsyncComponent = async () => {
await new Promise((r) => setTimeout(r, 1000)) // sleep 1s
return
Done!
}
app.get('/', (c) => {
return c.html(
)
})
```
## Suspense
The React-like `Suspense` feature is available.
If you wrap the async component with `Suspense`, the content in the fallback will be rendered first, and once the Promise is resolved, the awaited content will be displayed.
You can use it with `renderToReadableStream()`.
```tsx
import { renderToReadableStream, Suspense } from 'hono/jsx/streaming'
//...
app.get('/', (c) => {
const stream = renderToReadableStream(
loading...}>
)
return c.body(stream, {
headers: {
'Content-Type': 'text/html; charset=UTF-8',
'Transfer-Encoding': 'chunked',
},
})
})
```
## ErrorBoundary
You can catch errors in child components using `ErrorBoundary`.
In the example below, it will show the content specified in `fallback` if an error occurs.
```tsx
function SyncComponent() {
throw new Error('Error')
return
Hello
}
app.get('/sync', async (c) => {
return c.html(
Out of Service}>
)
})
```
`ErrorBoundary` can also be used with async components and `Suspense`.
```tsx
async function AsyncComponent() {
await new Promise((resolve) => setTimeout(resolve, 2000))
throw new Error('Error')
return
Hello
}
app.get('/with-suspense', async (c) => {
return c.html(
Out of Service}>
Loading...}>
)
})
```
## Integration with html Middleware
Combine the JSX and html middlewares for powerful templating.
For in-depth details, consult the [html middleware documentation](/docs/helpers/html).
```tsx
import { Hono } from 'hono'
import { html } from 'hono/html'
const app = new Hono()
interface SiteData {
title: string
children?: any
}
const Layout = (props: SiteData) =>
html`
${props.title}
${props.children}
`
const Content = (props: { siteData: SiteData; name: string }) => (
Hello {props.name}
)
app.get('/:name', (c) => {
const { name } = c.req.param()
const props = {
name: name,
siteData: {
title: 'JSX with html sample',
},
}
return c.html()
})
export default app
```
## With JSX Renderer Middleware
The [JSX Renderer Middleware](/docs/middleware/builtin/jsx-renderer) allows you to create HTML pages more easily with the JSX.
## Override type definitions
You can override the type definition to add your custom elements and attributes.
```ts
declare module 'hono/jsx' {
namespace JSX {
interface IntrinsicElements {
'my-custom-element': HTMLAttributes & {
'x-event'?: 'click' | 'scroll'
}
}
}
}
```
# Middleware
Middleware works after/before Handler. We can get `Request` before dispatching or manipulate `Response` after dispatching.
## Definition of Middleware
- Handler - should return `Response` object. Only one handler will be called.
- Middleware - should return nothing, will be proceeded to next middleware with `await next()`
The user can register middleware using `app.use` or using `app.HTTP_METHOD` as well as the handlers. For this feature, it's easy to specify the path and the method.
```ts
// match any method, all routes
app.use(logger())
// specify path
app.use('/posts/*', cors())
// specify method and path
app.post('/posts/*', basicAuth())
```
If the handler returns `Response`, it will be used for the end-user, and stopping the processing.
```ts
app.post('/posts', (c) => c.text('Created!', 201))
```
In this case, four middleware are processed before dispatching like this:
```ts
logger() -> cors() -> basicAuth() -> *handler*
```
## Execution order
The order in which Middleware is executed is determined by the order in which it is registered.
The process before the `next` of the first registered Middleware is executed first,
and the process after the `next` is executed last.
See below.
```ts
app.use(async (_, next) => {
console.log('middleware 1 start')
await next()
console.log('middleware 1 end')
})
app.use(async (_, next) => {
console.log('middleware 2 start')
await next()
console.log('middleware 2 end')
})
app.use(async (_, next) => {
console.log('middleware 3 start')
await next()
console.log('middleware 3 end')
})
app.get('/', (c) => {
console.log('handler')
return c.text('Hello!')
})
```
Result is the following.
```
middleware 1 start
middleware 2 start
middleware 3 start
handler
middleware 3 end
middleware 2 end
middleware 1 end
```
## Built-in Middleware
Hono has built-in middleware.
```ts
import { Hono } from 'hono'
import { poweredBy } from 'hono/powered-by'
import { logger } from 'hono/logger'
import { basicAuth } from 'hono/basic-auth'
const app = new Hono()
app.use(poweredBy())
app.use(logger())
app.use(
'/auth/*',
basicAuth({
username: 'hono',
password: 'acoolproject',
})
)
```
::: warning
In Deno, it is possible to use a different version of middleware than the Hono version, but this can lead to bugs.
For example, this code is not working because the version is different.
```ts
import { Hono } from 'jsr:@hono/hono@4.4.0'
import { upgradeWebSocket } from 'jsr:@hono/hono@4.4.5/deno'
const app = new Hono()
app.get(
'/ws',
upgradeWebSocket(() => ({
// ...
}))
)
```
:::
## Custom Middleware
You can write your own middleware directly inside `app.use()`:
```ts
// Custom logger
app.use(async (c, next) => {
console.log(`[${c.req.method}] ${c.req.url}`)
await next()
})
// Add a custom header
app.use('/message/*', async (c, next) => {
await next()
c.header('x-message', 'This is middleware!')
})
app.get('/message/hello', (c) => c.text('Hello Middleware!'))
```
However, embedding middleware directly within `app.use()` can limit its reusability. Therefore, we can separate our
middleware into different files.
To ensure we don't lose type definitions for `context` and `next`, when separating middleware, we can use
[`createMiddleware()`](/docs/helpers/factory#createmiddleware) from Hono's factory.
```ts
import { createMiddleware } from 'hono/factory'
const logger = createMiddleware(async (c, next) => {
console.log(`[${c.req.method}] ${c.req.url}`)
await next()
})
```
:::info
Type generics can be used with `createMiddleware`:
```ts
createMiddleware<{Bindings: Bindings}>(async (c, next) =>
```
:::
### Modify the Response After Next
Additionally, middleware can be designed to modify responses if necessary:
```ts
const stripRes = createMiddleware(async (c, next) => {
await next()
c.res = undefined
c.res = new Response('New Response')
})
```
## Context access inside Middleware arguments
To access the context inside middleware arguments, directly use the context parameter provided by `app.use`. See the example below for clarification.
```ts
import { cors } from 'hono/cors'
app.use('*', async (c, next) => {
const middleware = cors({
origin: c.env.CORS_ORIGIN,
})
return middleware(c, next)
})
```
### Extending the Context in Middleware
To extend the context inside middleware, use `c.set`. You can make this type-safe by passing a `{ Variables: { yourVariable: YourVariableType } }` generic argument to the `createMiddleware` function.
```ts
import { createMiddleware } from 'hono/factory'
const echoMiddleware = createMiddleware<{
Variables: {
echo: (str: string) => string
}
}>(async (c, next) => {
c.set('echo', (str) => str)
await next()
})
app.get('/echo', echoMiddleware, (c) => {
return c.text(c.var.echo('Hello!'))
})
```
## Third-party Middleware
Built-in middleware does not depend on external modules, but third-party middleware can depend on third-party libraries.
So with them, we may make a more complex application.
For example, we have GraphQL Server Middleware, Sentry Middleware, Firebase Auth Middleware, and others.
# Miscellaneous
## Contributing
Contributions Welcome! You can contribute in the following ways.
- Create an Issue - Propose a new feature. Report a bug.
- Pull Request - Fix a bug and typo. Refactor the code.
- Create third-party middleware - Instruct below.
- Share - Share your thoughts on the Blog, X(Twitter), and others.
- Make your application - Please try to use Hono.
For more details, see [Contribution Guide](https://github.com/honojs/hono/blob/main/docs/CONTRIBUTING.md).
## Sponsoring
You can sponsor Hono authors via the GitHub sponsor program.
- [Sponsor @yusukebe on GitHub Sponsors](https://github.com/sponsors/yusukebe)
- [Sponsor @usualoma on GitHub Sponsors](https://github.com/sponsors/usualoma)
## Other Resources
- GitHub repository: https://github.com/honojs
- npm registry: https://www.npmjs.com/package/hono
- JSR: https://jsr.io/@hono/hono
# RPC
The RPC feature allows sharing of the API specifications between the server and the client.
You can export the types of input type specified by the Validator and the output type emitted by `json()`. And Hono Client will be able to import it.
> [!NOTE]
> For the RPC types to work properly in a monorepo, in both the Client's and Server's tsconfig.json files, set `"strict": true` in `compilerOptions`. [Read more.](https://github.com/honojs/hono/issues/2270#issuecomment-2143745118)
## Server
All you need to do on the server side is to write a validator and create a variable `route`. The following example uses [Zod Validator](https://github.com/honojs/middleware/tree/main/packages/zod-validator).
```ts{1}
const route = app.post(
'/posts',
zValidator(
'form',
z.object({
title: z.string(),
body: z.string(),
})
),
(c) => {
// ...
return c.json(
{
ok: true,
message: 'Created!',
},
201
)
}
)
```
Then, export the type to share the API spec with the Client.
```ts
export type AppType = typeof route
```
## Client
On the Client side, import `hc` and `AppType` first.
```ts
import { AppType } from '.'
import { hc } from 'hono/client'
```
`hc` is a function to create a client. Pass `AppType` as Generics and specify the server URL as an argument.
```ts
const client = hc('http://localhost:8787/')
```
Call `client.{path}.{method}` and pass the data you wish to send to the server as an argument.
```ts
const res = await client.posts.$post({
form: {
title: 'Hello',
body: 'Hono is a cool project',
},
})
```
The `res` is compatible with the "fetch" Response. You can retrieve data from the server with `res.json()`.
```ts
if (res.ok) {
const data = await res.json()
console.log(data.message)
}
```
::: warning File Upload
Currently, the client does not support file uploading.
:::
## Status code
If you explicitly specify the status code, such as `200` or `404`, in `c.json()`. It will be added as a type for passing to the client.
```ts
// server.ts
const app = new Hono().get(
'/posts',
zValidator(
'query',
z.object({
id: z.string(),
})
),
async (c) => {
const { id } = c.req.valid('query')
const post: Post | undefined = await getPost(id)
if (post === undefined) {
return c.json({ error: 'not found' }, 404) // Specify 404
}
return c.json({ post }, 200) // Specify 200
}
)
export type AppType = typeof app
```
You can get the data by the status code.
```ts
// client.ts
const client = hc('http://localhost:8787/')
const res = await client.posts.$get({
query: {
id: '123',
},
})
if (res.status === 404) {
const data: { error: string } = await res.json()
console.log(data.error)
}
if (res.ok) {
const data: { post: Post } = await res.json()
console.log(data.post)
}
// { post: Post } | { error: string }
type ResponseType = InferResponseType
// { post: Post }
type ResponseType200 = InferResponseType<
typeof client.posts.$get,
200
>
```
## Not Found
If you want to use a client, you should not use `c.notFound()` for the Not Found response. The data that the client gets from the server cannot be inferred correctly.
```ts
// server.ts
export const routes = new Hono().get(
'/posts',
zValidator(
'query',
z.object({
id: z.string(),
})
),
async (c) => {
const { id } = c.req.valid('query')
const post: Post | undefined = await getPost(id)
if (post === undefined) {
return c.notFound() // ❌️
}
return c.json({ post })
}
)
// client.ts
import { hc } from 'hono/client'
const client = hc('/')
const res = await client.posts[':id'].$get({
param: {
id: '123',
},
})
const data = await res.json() // 🙁 data is unknown
```
Please use `c.json()` and specify the status code for the Not Found Response.
```ts
export const routes = new Hono().get(
'/posts',
zValidator(
'query',
z.object({
id: z.string(),
})
),
async (c) => {
const { id } = c.req.valid('query')
const post: Post | undefined = await getPost(id)
if (post === undefined) {
return c.json({ error: 'not found' }, 404) // Specify 404
}
return c.json({ post }, 200) // Specify 200
}
)
```
## Path parameters
You can also handle routes that include path parameters.
```ts
const route = app.get(
'/posts/:id',
zValidator(
'query',
z.object({
page: z.string().optional(),
})
),
(c) => {
// ...
return c.json({
title: 'Night',
body: 'Time to sleep',
})
}
)
```
Specify the string you want to include in the path with `param`.
```ts
const res = await client.posts[':id'].$get({
param: {
id: '123',
},
query: {},
})
```
## Headers
You can append the headers to the request.
```ts
const res = await client.search.$get(
{
//...
},
{
headers: {
'X-Custom-Header': 'Here is Hono Client',
'X-User-Agent': 'hc',
},
}
)
```
To add a common header to all requests, specify it as an argument to the `hc` function.
```ts
const client = hc('/api', {
headers: {
Authorization: 'Bearer TOKEN',
},
})
```
## `init` option
You can pass the fetch's `RequestInit` object to the request as the `init` option. Below is an example of aborting a Request.
```ts
import { hc } from 'hono/client'
const client = hc('http://localhost:8787/')
const abortController = new AbortController()
const res = await client.api.posts.$post(
{
json: {
// Request body
},
},
{
// RequestInit object
init: {
signal: abortController.signal,
},
}
)
// ...
abortController.abort()
```
::: info
A `RequestInit` object defined by `init` takes the highest priority. It could be used to overwrite things set by other options like `body | method | headers`.
:::
## `$url()`
You can get a `URL` object for accessing the endpoint by using `$url()`.
::: warning
You have to pass in an absolute URL for this to work. Passing in a relative URL `/` will result in the following error.
`Uncaught TypeError: Failed to construct 'URL': Invalid URL`
```ts
// ❌ Will throw error
const client = hc('/')
client.api.post.$url()
// ✅ Will work as expected
const client = hc('http://localhost:8787/')
client.api.post.$url()
```
:::
```ts
const route = app
.get('/api/posts', (c) => c.json({ posts }))
.get('/api/posts/:id', (c) => c.json({ post }))
const client = hc('http://localhost:8787/')
let url = client.api.posts.$url()
console.log(url.pathname) // `/api/posts`
url = client.api.posts[':id'].$url({
param: {
id: '123',
},
})
console.log(url.pathname) // `/api/posts/123`
```
## Custom `fetch` method
You can set the custom `fetch` method.
In the following example script for Cloudflare Worker, the Service Bindings' `fetch` method is used instead of the default `fetch`.
```toml
# wrangler.toml
services = [
{ binding = "AUTH", service = "auth-service" },
]
```
```ts
// src/client.ts
const client = hc('/', {
fetch: c.env.AUTH.fetch.bind(c.env.AUTH),
})
```
## Infer
Use `InferRequestType` and `InferResponseType` to know the type of object to be requested and the type of object to be returned.
```ts
import type { InferRequestType, InferResponseType } from 'hono/client'
// InferRequestType
const $post = client.todo.$post
type ReqType = InferRequestType['form']
// InferResponseType
type ResType = InferResponseType
```
## Using SWR
You can also use a React Hook library such as [SWR](https://swr.vercel.app).
```tsx
import useSWR from 'swr'
import { hc } from 'hono/client'
import type { InferRequestType } from 'hono/client'
import { AppType } from '../functions/api/[[route]]'
const App = () => {
const client = hc('/api')
const $get = client.hello.$get
const fetcher =
(arg: InferRequestType) => async () => {
const res = await $get(arg)
return await res.json()
}
const { data, error, isLoading } = useSWR(
'api-hello',
fetcher({
query: {
name: 'SWR',
},
})
)
if (error) return
failed to load
if (isLoading) return
loading...
return
{data?.message}
}
export default App
```
## Using RPC with larger applications
In the case of a larger application, such as the example mentioned in [Building a larger application](/docs/guides/best-practices#building-a-larger-application), you need to be careful about the type of inference.
A simple way to do this is to chain the handlers so that the types are always inferred.
```ts
// authors.ts
import { Hono } from 'hono'
const app = new Hono()
.get('/', (c) => c.json('list authors'))
.post('/', (c) => c.json('create an author', 201))
.get('/:id', (c) => c.json(`get ${c.req.param('id')}`))
export default app
```
```ts
// books.ts
import { Hono } from 'hono'
const app = new Hono()
.get('/', (c) => c.json('list books'))
.post('/', (c) => c.json('create a book', 201))
.get('/:id', (c) => c.json(`get ${c.req.param('id')}`))
export default app
```
You can then import the sub-routers as you usually would, and make sure you chain their handlers as well, since this is the top level of the app in this case, this is the type we'll want to export.
```ts
// index.ts
import { Hono } from 'hono'
import authors from './authors'
import books from './books'
const app = new Hono()
const routes = app.route('/authors', authors).route('/books', books)
export default app
export type AppType = typeof routes
```
You can now create a new client using the registered AppType and use it as you would normally.
## Known issues
### IDE performance
When using RPC, the more routes you have, the slower your IDE will become. One of the main reasons for this is that massive amounts of type instantiations are executed to infer the type of your app.
For example, suppose your app has a route like this:
```ts
// app.ts
export const app = new Hono().get('foo/:id', (c) =>
c.json({ ok: true }, 200)
)
```
Hono will infer the type as follows:
```ts
export const app = Hono().get<
'foo/:id',
'foo/:id',
JSONRespondReturn<{ ok: boolean }, 200>,
BlankInput,
BlankEnv
>('foo/:id', (c) => c.json({ ok: true }, 200))
```
This is a type instantiation for a single route. While the user doesn't need to write these type arguments manually, which is a good thing, it's known that type instantiation takes much time. `tsserver` used in your IDE does this time consuming task every time you use the app. If you have a lot of routes, this can slow down your IDE significantly.
However, we have some tips to mitigate this issue.
#### Hono version mismatch
If your backend is separate from the frontend and lives in a different directory, you need to ensure that the Hono versions match. If you use one Hono version on the backend and another on the frontend, you'll run into issues such as "_Type instantiation is excessively deep and possibly infinite_".
#### TypeScript project references
Like in the case of [Hono version mismatch](#hono-version-mismatch), you'll run into issues if your backend and frontend are separate. If you want to access code from the backend (`AppType`, for example) on the frontend, you need to use [project references](https://www.typescriptlang.org/docs/handbook/project-references.html). TypeScript's project references allow one TypeScript codebase to access and use code from another TypeScript codebase. _(source: [Hono RPC And TypeScript Project References](https://catalins.tech/hono-rpc-in-monorepos/))_.
#### Compile your code before using it (recommended)
`tsc` can do heavy tasks like type instantiation at compile time! Then, `tsserver` doesn't need to instantiate all the type arguments every time you use it. It will make your IDE a lot faster!
Compiling your client including the server app gives you the best performance. Put the following code in your project:
```ts
import { app } from './app'
import { hc } from 'hono/client'
// this is a trick to calculate the type when compiling
const client = hc('')
export type Client = typeof client
export const hcWithType = (...args: Parameters): Client =>
hc(...args)
```
After compiling, you can use `hcWithType` instead of `hc` to get the client with the type already calculated.
```ts
const client = hcWithType('http://localhost:8787/')
const res = await client.posts.$post({
form: {
title: 'Hello',
body: 'Hono is a cool project',
},
})
```
If your project is a monorepo, this solution does fit well. Using a tool like [`turborepo`](https://turbo.build/repo/docs), you can easily separate the server project and the client project and get better integration managing dependencies between them. Here is [a working example](https://github.com/m-shaka/hono-rpc-perf-tips-example).
You can also coordinate your build process manually with tools like `concurrently` or `npm-run-all`.
#### Specify type arguments manually
This is a bit cumbersome, but you can specify type arguments manually to avoid type instantiation.
```ts
const app = new Hono().get<'foo/:id'>('foo/:id', (c) =>
c.json({ ok: true }, 200)
)
```
Specifying just single type argument make a difference in performance, while it may take you a lot of time and effort if you have a lot of routes.
#### Split your app and client into multiple files
As described in [Using RPC with larger applications](#using-rpc-with-larger-applications), you can split your app into multiple apps. You can also create a client for each app:
```ts
// authors-cli.ts
import { app as authorsApp } from './authors'
import { hc } from 'hono/client'
const authorsClient = hc('/authors')
// books-cli.ts
import { app as booksApp } from './books'
import { hc } from 'hono/client'
const booksClient = hc('/books')
```
This way, `tsserver` doesn't need to instantiate types for all routes at once.
# Testing
Testing is important.
In actuality, it is easy to test Hono's applications.
The way to create a test environment differs from each runtime, but the basic steps are the same.
In this section, let's test with Cloudflare Workers and Jest.
## Request and Response
All you do is create a Request and pass it to the Hono application to validate the Response.
And, you can use `app.request` the useful method.
::: tip
For a typed test client see the [testing helper](/docs/helpers/testing).
:::
For example, consider an application that provides the following REST API.
```ts
app.get('/posts', (c) => {
return c.text('Many posts')
})
app.post('/posts', (c) => {
return c.json(
{
message: 'Created',
},
201,
{
'X-Custom': 'Thank you',
}
)
})
```
Make a request to `GET /posts` and test the response.
```ts
describe('Example', () => {
test('GET /posts', async () => {
const res = await app.request('/posts')
expect(res.status).toBe(200)
expect(await res.text()).toBe('Many posts')
})
})
```
To make a request to `POST /posts`, do the following.
```ts
test('POST /posts', async () => {
const res = await app.request('/posts', {
method: 'POST',
})
expect(res.status).toBe(201)
expect(res.headers.get('X-Custom')).toBe('Thank you')
expect(await res.json()).toEqual({
message: 'Created',
})
})
```
To make a request to `POST /posts` with `JSON` data, do the following.
```ts
test('POST /posts', async () => {
const res = await app.request('/posts', {
method: 'POST',
body: JSON.stringify({ message: 'hello hono' }),
headers: new Headers({ 'Content-Type': 'application/json' }),
})
expect(res.status).toBe(201)
expect(res.headers.get('X-Custom')).toBe('Thank you')
expect(await res.json()).toEqual({
message: 'Created',
})
})
```
To make a request to `POST /posts` with `multipart/form-data` data, do the following.
```ts
test('POST /posts', async () => {
const formData = new FormData()
formData.append('message', 'hello')
const res = await app.request('/posts', {
method: 'POST',
body: formData,
})
expect(res.status).toBe(201)
expect(res.headers.get('X-Custom')).toBe('Thank you')
expect(await res.json()).toEqual({
message: 'Created',
})
})
```
You can also pass an instance of the Request class.
```ts
test('POST /posts', async () => {
const req = new Request('http://localhost/posts', {
method: 'POST',
})
const res = await app.request(req)
expect(res.status).toBe(201)
expect(res.headers.get('X-Custom')).toBe('Thank you')
expect(await res.json()).toEqual({
message: 'Created',
})
})
```
In this way, you can test it as like an End-to-End.
## Env
To set `c.env` for testing, you can pass it as the 3rd parameter to `app.request`. This is useful for mocking values like [Cloudflare Workers Bindings](https://hono.dev/getting-started/cloudflare-workers#bindings):
```ts
const MOCK_ENV = {
API_HOST: 'example.com',
DB: {
prepare: () => {
/* mocked D1 */
},
},
}
test('GET /posts', async () => {
const res = await app.request('/posts', {}, MOCK_ENV)
})
```
# Validation
Hono provides only a very thin Validator.
But, it can be powerful when combined with a third-party Validator.
In addition, the RPC feature allows you to share API specifications with your clients through types.
## Manual validator
First, introduce a way to validate incoming values without using the third-party Validator.
Import `validator` from `hono/validator`.
```ts
import { validator } from 'hono/validator'
```
To validate form data, specify `form` as the first argument and a callback as the second argument.
In the callback, validates the value and return the validated values at the end.
The `validator` can be used as middleware.
```ts
app.post(
'/posts',
validator('form', (value, c) => {
const body = value['body']
if (!body || typeof body !== 'string') {
return c.text('Invalid!', 400)
}
return {
body: body,
}
}),
//...
```
Within the handler you can get the validated value with `c.req.valid('form')`.
```ts
, (c) => {
const { body } = c.req.valid('form')
// ... do something
return c.json(
{
message: 'Created!',
},
201
)
}
```
Validation targets include `json`, `query`, `header`, `param` and `cookie` in addition to `form`.
::: warning
When you validate `json`, the request _must_ contain a `Content-Type: application/json` header
otherwise the request body will not be parsed and you will receive a warning.
It is important to set the `content-type` header when testing using
[`app.request()`](../api/request.md).
Given an application like this.
```ts
const app = new Hono()
app.post(
'/testing',
validator('json', (value, c) => {
// pass-through validator
return value
}),
(c) => {
const body = c.req.valid('json')
return c.json(body)
}
)
```
Your tests can be written like this.
```ts
// ❌ this will not work
const res = await app.request('/testing', {
method: 'POST',
body: JSON.stringify({ key: 'value' }),
})
const data = await res.json()
console.log(data) // undefined
// ✅ this will work
const res = await app.request('/testing', {
method: 'POST',
body: JSON.stringify({ key: 'value' }),
headers: new Headers({ 'Content-Type': 'application/json' }),
})
const data = await res.json()
console.log(data) // { key: 'value' }
```
:::
::: warning
When you validate `header`, you need to use **lowercase** name as the key.
If you want to validate the `Idempotency-Key` header, you need to use `idempotency-key` as the key.
```ts
// ❌ this will not work
app.post(
'/api',
validator('header', (value, c) => {
// idempotencyKey is always undefined
// so this middleware always return 400 as not expected
const idempotencyKey = value['Idempotency-Key']
if (idempotencyKey == undefined || idempotencyKey === '') {
throw HTTPException(400, {
message: 'Idempotency-Key is required',
})
}
return { idempotencyKey }
}),
(c) => {
const { idempotencyKey } = c.req.valid('header')
// ...
}
)
// ✅ this will work
app.post(
'/api',
validator('header', (value, c) => {
// can retrieve the value of the header as expected
const idempotencyKey = value['idempotency-key']
if (idempotencyKey == undefined || idempotencyKey === '') {
throw HTTPException(400, {
message: 'Idempotency-Key is required',
})
}
return { idempotencyKey }
}),
(c) => {
const { idempotencyKey } = c.req.valid('header')
// ...
}
)
```
:::
## Multiple validators
You can also include multiple validators to validate different parts of request:
```ts
app.post(
'/posts/:id',
validator('param', ...),
validator('query', ...),
validator('json', ...),
(c) => {
//...
}
```
## With Zod
You can use [Zod](https://zod.dev), one of third-party validators.
We recommend using a third-party validator.
Install from the Npm registry.
::: code-group
```sh [npm]
npm i zod
```
```sh [yarn]
yarn add zod
```
```sh [pnpm]
pnpm add zod
```
```sh [bun]
bun add zod
```
:::
Import `z` from `zod`.
```ts
import { z } from 'zod'
```
Write your schema.
```ts
const schema = z.object({
body: z.string(),
})
```
You can use the schema in the callback function for validation and return the validated value.
```ts
const route = app.post(
'/posts',
validator('form', (value, c) => {
const parsed = schema.safeParse(value)
if (!parsed.success) {
return c.text('Invalid!', 401)
}
return parsed.data
}),
(c) => {
const { body } = c.req.valid('form')
// ... do something
return c.json(
{
message: 'Created!',
},
201
)
}
)
```
## Zod Validator Middleware
You can use the [Zod Validator Middleware](https://github.com/honojs/middleware/tree/main/packages/zod-validator) to make it even easier.
::: code-group
```sh [npm]
npm i @hono/zod-validator
```
```sh [yarn]
yarn add @hono/zod-validator
```
```sh [pnpm]
pnpm add @hono/zod-validator
```
```sh [bun]
bun add @hono/zod-validator
```
:::
And import `zValidator`.
```ts
import { zValidator } from '@hono/zod-validator'
```
And write as follows.
```ts
const route = app.post(
'/posts',
zValidator(
'form',
z.object({
body: z.string(),
})
),
(c) => {
const validated = c.req.valid('form')
// ... use your validated data
}
)
```
# Alibaba Cloud Function Compute
[Alibaba Cloud Function Compute](https://www.alibabacloud.com/en/product/function-compute) is a fully managed, event-driven compute service. Function Compute allows you to focus on writing and uploading code without having to manage infrastructure such as servers.
This guide uses a third-party adapter [rwv/hono-alibaba-cloud-fc3-adapter](https://github.com/rwv/hono-alibaba-cloud-fc3-adapter) to run Hono on Alibaba Cloud Function Compute.
## 1. Setup
::: code-group
```sh [npm]
mkdir my-app
cd my-app
npm i hono hono-alibaba-cloud-fc3-adapter
npm i -D @serverless-devs/s esbuild
mkdir src
touch src/index.ts
```
```sh [yarn]
mkdir my-app
cd my-app
yarn add hono hono-alibaba-cloud-fc3-adapter
yarn add -D @serverless-devs/s esbuild
mkdir src
touch src/index.ts
```
```sh [pnpm]
mkdir my-app
cd my-app
pnpm add hono hono-alibaba-cloud-fc3-adapter
pnpm add -D @serverless-devs/s esbuild
mkdir src
touch src/index.ts
```
```sh [bun]
mkdir my-app
cd my-app
bun add hono hono-alibaba-cloud-fc3-adapter
bun add -D esbuild @serverless-devs/s
mkdir src
touch src/index.ts
```
:::
## 2. Hello World
Edit `src/index.ts`.
```ts
import { Hono } from 'hono'
import { handle } from 'hono-alibaba-cloud-fc3-adapter'
const app = new Hono()
app.get('/', (c) => c.text('Hello Hono!'))
export const handler = handle(app)
```
## 3. Setup serverless-devs
> [serverless-devs](https://github.com/Serverless-Devs/Serverless-Devs) is an open source and open serverless developer platform dedicated to providing developers with a powerful tool chain system. Through this platform, developers can not only experience multi cloud serverless products with one click and rapidly deploy serverless projects, but also manage projects in the whole life cycle of serverless applications, and combine serverless devs with other tools / platforms very simply and quickly to further improve the efficiency of R & D, operation and maintenance.
Add the Alibaba Cloud AccessKeyID & AccessKeySecret
```sh
npx s config add
# Please select a provider: Alibaba Cloud (alibaba)
# Input your AccessKeyID & AccessKeySecret
```
Edit `s.yaml`
```yaml
edition: 3.0.0
name: my-app
access: 'default'
vars:
region: 'us-west-1'
resources:
my-app:
component: fc3
props:
region: ${vars.region}
functionName: 'my-app'
description: 'Hello World by Hono'
runtime: 'nodejs20'
code: ./dist
handler: index.handler
memorySize: 1024
timeout: 300
```
Edit `scripts` section in `package.json`:
```json
{
"scripts": {
"build": "esbuild --bundle --outfile=./dist/index.js --platform=node --target=node20 ./src/index.ts",
"deploy": "s deploy -y"
}
}
```
## 4. Deploy
Finally, run the command to deploy:
```sh
npm run build # Compile the TypeScript code to JavaScript
npm run deploy # Deploy the function to Alibaba Cloud Function Compute
```
# AWS Lambda
AWS Lambda is a serverless platform by Amazon Web Services.
You can run your code in response to events and automatically manages the underlying compute resources for you.
Hono works on AWS Lambda with the Node.js 18+ environment.
## 1. Setup
When creating the application on AWS Lambda,
[CDK](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-cdk.html)
is useful to setup the functions such as IAM Role, API Gateway, and others.
Initialize your project with the `cdk` CLI.
::: code-group
```sh [npm]
mkdir my-app
cd my-app
cdk init app -l typescript
npm i hono
mkdir lambda
touch lambda/index.ts
```
```sh [yarn]
mkdir my-app
cd my-app
cdk init app -l typescript
yarn add hono
mkdir lambda
touch lambda/index.ts
```
```sh [pnpm]
mkdir my-app
cd my-app
cdk init app -l typescript
pnpm add hono
mkdir lambda
touch lambda/index.ts
```
```sh [bun]
mkdir my-app
cd my-app
cdk init app -l typescript
bun add hono
mkdir lambda
touch lambda/index.ts
```
:::
## 2. Hello World
Edit `lambda/index.ts`.
```ts
import { Hono } from 'hono'
import { handle } from 'hono/aws-lambda'
const app = new Hono()
app.get('/', (c) => c.text('Hello Hono!'))
export const handler = handle(app)
```
## 3. Deploy
Edit `lib/cdk-stack.ts`.
```ts
import * as cdk from 'aws-cdk-lib'
import { Construct } from 'constructs'
import * as lambda from 'aws-cdk-lib/aws-lambda'
import * as apigw from 'aws-cdk-lib/aws-apigateway'
import { NodejsFunction } from 'aws-cdk-lib/aws-lambda-nodejs'
export class MyAppStack extends cdk.Stack {
constructor(scope: Construct, id: string, props?: cdk.StackProps) {
super(scope, id, props)
const fn = new NodejsFunction(this, 'lambda', {
entry: 'lambda/index.ts',
handler: 'handler',
runtime: lambda.Runtime.NODEJS_20_X,
})
fn.addFunctionUrl({
authType: lambda.FunctionUrlAuthType.NONE,
})
new apigw.LambdaRestApi(this, 'myapi', {
handler: fn,
})
}
}
```
Finally, run the command to deploy:
```sh
cdk deploy
```
## Serve Binary data
Hono supports binary data as a response.
In Lambda, base64 encoding is required to return binary data.
Once binary type is set to `Content-Type` header, Hono automatically encodes data to base64.
```ts
app.get('/binary', async (c) => {
// ...
c.status(200)
c.header('Content-Type', 'image/png') // means binary data
return c.body(buffer) // supports `ArrayBufferLike` type, encoded to base64.
})
```
## Access AWS Lambda Object
In Hono, you can access the AWS Lambda Events and Context by binding the `LambdaEvent`, `LambdaContext` type and using `c.env`
```ts
import { Hono } from 'hono'
import type { LambdaEvent, LambdaContext } from 'hono/aws-lambda'
import { handle } from 'hono/aws-lambda'
type Bindings = {
event: LambdaEvent
lambdaContext: LambdaContext
}
const app = new Hono<{ Bindings: Bindings }>()
app.get('/aws-lambda-info/', (c) => {
return c.json({
isBase64Encoded: c.env.event.isBase64Encoded,
awsRequestId: c.env.lambdaContext.awsRequestId,
})
})
export const handler = handle(app)
```
## Access RequestContext
In Hono, you can access the AWS Lambda request context by binding the `LambdaEvent` type and using `c.env.event.requestContext`.
```ts
import { Hono } from 'hono'
import type { LambdaEvent } from 'hono/aws-lambda'
import { handle } from 'hono/aws-lambda'
type Bindings = {
event: LambdaEvent
}
const app = new Hono<{ Bindings: Bindings }>()
app.get('/custom-context/', (c) => {
const lambdaContext = c.env.event.requestContext
return c.json(lambdaContext)
})
export const handler = handle(app)
```
### Before v3.10.0 (deprecated)
you can access the AWS Lambda request context by binding the `ApiGatewayRequestContext` type and using `c.env.`
```ts
import { Hono } from 'hono'
import type { ApiGatewayRequestContext } from 'hono/aws-lambda'
import { handle } from 'hono/aws-lambda'
type Bindings = {
requestContext: ApiGatewayRequestContext
}
const app = new Hono<{ Bindings: Bindings }>()
app.get('/custom-context/', (c) => {
const lambdaContext = c.env.requestContext
return c.json(lambdaContext)
})
export const handler = handle(app)
```
## Lambda response streaming
By changing the invocation mode of AWS Lambda, you can achieve [Streaming Response](https://aws.amazon.com/blogs/compute/introducing-aws-lambda-response-streaming/).
```diff
fn.addFunctionUrl({
authType: lambda.FunctionUrlAuthType.NONE,
+ invokeMode: lambda.InvokeMode.RESPONSE_STREAM,
})
```
Typically, the implementation requires writing chunks to NodeJS.WritableStream using awslambda.streamifyResponse, but with the AWS Lambda Adaptor, you can achieve the traditional streaming response of Hono by using streamHandle instead of handle.
```ts
import { Hono } from 'hono'
import { streamHandle } from 'hono/aws-lambda'
const app = new Hono()
app.get('/stream', async (c) => {
return streamText(c, async (stream) => {
for (let i = 0; i < 3; i++) {
await stream.writeln(`${i}`)
await stream.sleep(1)
}
})
})
const handler = streamHandle(app)
```
# Azure Functions
[Azure Functions](https://azure.microsoft.com/en-us/products/functions) is a serverless platform from Microsoft Azure. You can run your code in response to events, and it automatically manages the underlying compute resources for you.
Hono was not designed for Azure Functions at first. But with [Azure Functions Adapter](https://github.com/Marplex/hono-azurefunc-adapter) it can run on it as well.
It works with Azure Functions **V4** running on Node.js 18 or above.
## 1. Install CLI
To create an Azure Function, you must first install [Azure Functions Core Tools](https://learn.microsoft.com/en-us/azure/azure-functions/create-first-function-cli-typescript?pivots=nodejs-model-v4#install-the-azure-functions-core-tools).
On macOS
```sh
brew tap azure/functions
brew install azure-functions-core-tools@4
```
Follow this link for other OS:
- [Install the Azure Functions Core Tools | Microsoft Learn](https://learn.microsoft.com/en-us/azure/azure-functions/create-first-function-cli-typescript?pivots=nodejs-model-v4#install-the-azure-functions-core-tools)
## 2. Setup
Create a TypeScript Node.js V4 project in the current folder.
```sh
func init --typescript
```
Change the default route prefix of the host. Add this property to the root json object of `host.json`:
```json
"extensions": {
"http": {
"routePrefix": ""
}
}
```
::: info
The default Azure Functions route prefix is `/api`. If you don't change it as shown above, be sure to start all your Hono routes with `/api`
:::
Now you are ready to install Hono and the Azure Functions Adapter with:
::: code-group
```sh [npm]
npm i @marplex/hono-azurefunc-adapter hono
```
```sh [yarn]
yarn add @marplex/hono-azurefunc-adapter hono
```
```sh [pnpm]
pnpm add @marplex/hono-azurefunc-adapter hono
```
```sh [bun]
bun add @marplex/hono-azurefunc-adapter hono
```
:::
## 3. Hello World
Create `src/app.ts`:
```ts
// src/app.ts
import { Hono } from 'hono'
const app = new Hono()
app.get('/', (c) => c.text('Hello Azure Functions!'))
export default app
```
Create `src/functions/httpTrigger.ts`:
```ts
// src/functions/httpTrigger.ts
import { app } from '@azure/functions'
import { azureHonoHandler } from '@marplex/hono-azurefunc-adapter'
import honoApp from '../app'
app.http('httpTrigger', {
methods: [
//Add all your supported HTTP methods here
'GET',
'POST',
'DELETE',
'PUT',
],
authLevel: 'anonymous',
route: '{*proxy}',
handler: azureHonoHandler(honoApp.fetch),
})
```
## 4. Run
Run the development server locally. Then, access `http://localhost:7071` in your Web browser.
::: code-group
```sh [npm]
npm run start
```
```sh [yarn]
yarn start
```
```sh [pnpm]
pnpm start
```
```sh [bun]
bun run start
```
:::
## 5. Deploy
::: info
Before you can deploy to Azure, you need to create some resources in your cloud infrastructure. Please visit the Microsoft documentation on [Create supporting Azure resources for your function](https://learn.microsoft.com/en-us/azure/azure-functions/create-first-function-cli-typescript?pivots=nodejs-model-v4&tabs=windows%2Cazure-cli%2Cbrowser#create-supporting-azure-resources-for-your-function)
:::
Build the project for deployment:
::: code-group
```sh [npm]
npm run build
```
```sh [yarn]
yarn build
```
```sh [pnpm]
pnpm build
```
```sh [bun]
bun run build
```
:::
Deploy your project to the function app in Azure Cloud. Replace `` with the name of your app.
```sh
func azure functionapp publish
```
# Getting Started
Using Hono is super easy. We can set up the project, write code, develop with a local server, and deploy quickly. The same code will work on any runtime, just with different entry points. Let's look at the basic usage of Hono.
## Starter
Starter templates are available for each platform. Use the following "create-hono" command.
::: code-group
```sh [npm]
npm create hono@latest my-app
```
```sh [yarn]
yarn create hono my-app
```
```sh [pnpm]
pnpm create hono@latest my-app
```
```sh [bun]
bun create hono@latest my-app
```
```sh [deno]
deno init --npm hono@latest my-app
```
:::
Then you will be asked which template you would like to use.
Let's select Cloudflare Workers for this example.
```
? Which template do you want to use?
aws-lambda
bun
cloudflare-pages
❯ cloudflare-workers
deno
fastly
nextjs
nodejs
vercel
```
The template will be pulled into `my-app`, so go to it and install the dependencies.
::: code-group
```sh [npm]
cd my-app
npm i
```
```sh [yarn]
cd my-app
yarn
```
```sh [pnpm]
cd my-app
pnpm i
```
```sh [bun]
cd my-app
bun i
```
:::
Once the package installation is complete, run the following command to start up a local server.
::: code-group
```sh [npm]
npm run dev
```
```sh [yarn]
yarn dev
```
```sh [pnpm]
pnpm dev
```
```sh [bun]
bun run dev
```
:::
## Hello World
You can write code in TypeScript with the Cloudflare Workers development tool "Wrangler", Deno, Bun, or others without being aware of transpiling.
Write your first application with Hono in `src/index.ts`. The example below is a starter Hono application.
The `import` and the final `export default` parts may vary from runtime to runtime,
but all of the application code will run the same code everywhere.
```ts
import { Hono } from 'hono'
const app = new Hono()
app.get('/', (c) => {
return c.text('Hello Hono!')
})
export default app
```
Start the development server and access `http://localhost:8787` with your browser.
::: code-group
```sh [npm]
npm run dev
```
```sh [yarn]
yarn dev
```
```sh [pnpm]
pnpm dev
```
```sh [bun]
bun run dev
```
:::
## Return JSON
Returning JSON is also easy. The following is an example of handling a GET Request to `/api/hello` and returning an `application/json` Response.
```ts
app.get('/api/hello', (c) => {
return c.json({
ok: true,
message: 'Hello Hono!',
})
})
```
## Request and Response
Getting a path parameter, URL query value, and appending a Response header is written as follows.
```ts
app.get('/posts/:id', (c) => {
const page = c.req.query('page')
const id = c.req.param('id')
c.header('X-Message', 'Hi!')
return c.text(`You want to see ${page} of ${id}`)
})
```
We can easily handle POST, PUT, and DELETE not only GET.
```ts
app.post('/posts', (c) => c.text('Created!', 201))
app.delete('/posts/:id', (c) =>
c.text(`${c.req.param('id')} is deleted!`)
)
```
## Return HTML
You can write HTML with [the html Helper](/docs/helpers/html) or using [JSX](/docs/guides/jsx) syntax. If you want to use JSX, rename the file to `src/index.tsx` and configure it (check with each runtime as it is different). Below is an example using JSX.
```tsx
const View = () => {
return (
Hello Hono!
)
}
app.get('/page', (c) => {
return c.html()
})
```
## Return raw Response
You can also return the raw [Response](https://developer.mozilla.org/en-US/docs/Web/API/Response).
```ts
app.get('/', () => {
return new Response('Good morning!')
})
```
## Using Middleware
Middleware can do the hard work for you.
For example, add in Basic Authentication.
```ts
import { basicAuth } from 'hono/basic-auth'
// ...
app.use(
'/admin/*',
basicAuth({
username: 'admin',
password: 'secret',
})
)
app.get('/admin', (c) => {
return c.text('You are authorized!')
})
```
There are useful built-in middleware including Bearer and authentication using JWT, CORS and ETag.
Hono also provides third-party middleware using external libraries such as GraphQL Server and Firebase Auth.
And, you can make your own middleware.
## Adapter
There are Adapters for platform-dependent functions, e.g., handling static files or WebSocket.
For example, to handle WebSocket in Cloudflare Workers, import `hono/cloudflare-workers`.
```ts
import { upgradeWebSocket } from 'hono/cloudflare-workers'
app.get(
'/ws',
upgradeWebSocket((c) => {
// ...
})
)
```
## Next step
Most code will work on any platform, but there are guides for each.
For instance, how to set up projects or how to deploy.
Please see the page for the exact platform you want to use to create your application!
# Bun
[Bun](https://bun.sh) is another JavaScript runtime. It's not Node.js or Deno. Bun includes a trans compiler, we can write the code with TypeScript.
Hono also works on Bun.
## 1. Install Bun
To install `bun` command, follow the instruction in [the official web site](https://bun.sh).
## 2. Setup
### 2.1. Setup a new project
A starter for Bun is available. Start your project with "bun create" command.
Select `bun` template for this example.
```sh
bun create hono@latest my-app
```
Move into my-app and install the dependencies.
```sh
cd my-app
bun install
```
### 2.2. Setup an existing project
On an existing Bun project, we only need to install `hono` dependencies on the project root directory via
```sh
bun add hono
```
## 3. Hello World
"Hello World" script is below. Almost the same as writing on other platforms.
```ts
import { Hono } from 'hono'
const app = new Hono()
app.get('/', (c) => c.text('Hello Bun!'))
export default app
```
## 4. Run
Run the command.
```sh
bun run dev
```
Then, access `http://localhost:3000` in your browser.
## Change port number
You can specify the port number with exporting the `port`.
```ts
import { Hono } from 'hono'
const app = new Hono()
app.get('/', (c) => c.text('Hello Bun!'))
export default app // [!code --]
export default { // [!code ++]
port: 3000, // [!code ++]
fetch: app.fetch, // [!code ++]
} // [!code ++]
```
## Serve static files
To serve static files, use `serveStatic` imported from `hono/bun`.
```ts
import { serveStatic } from 'hono/bun'
const app = new Hono()
app.use('/static/*', serveStatic({ root: './' }))
app.use('/favicon.ico', serveStatic({ path: './favicon.ico' }))
app.get('/', (c) => c.text('You can access: /static/hello.txt'))
app.get('*', serveStatic({ path: './static/fallback.txt' }))
```
For the above code, it will work well with the following directory structure.
```
./
├── favicon.ico
├── src
└── static
├── demo
│ └── index.html
├── fallback.txt
├── hello.txt
└── images
└── dinotocat.png
```
### `rewriteRequestPath`
If you want to map `http://localhost:3000/static/*` to `./statics`, you can use the `rewriteRequestPath` option:
```ts
app.get(
'/static/*',
serveStatic({
root: './',
rewriteRequestPath: (path) =>
path.replace(/^\/static/, '/statics'),
})
)
```
### `mimes`
You can add MIME types with `mimes`:
```ts
app.get(
'/static/*',
serveStatic({
mimes: {
m3u8: 'application/vnd.apple.mpegurl',
ts: 'video/mp2t',
},
})
)
```
### `onFound`
You can specify handling when the requested file is found with `onFound`:
```ts
app.get(
'/static/*',
serveStatic({
// ...
onFound: (_path, c) => {
c.header('Cache-Control', `public, immutable, max-age=31536000`)
},
})
)
```
### `onNotFound`
You can specify handling when the requested file is not found with `onNotFound`:
```ts
app.get(
'/static/*',
serveStatic({
onNotFound: (path, c) => {
console.log(`${path} is not found, you access ${c.req.path}`)
},
})
)
```
### `precompressed`
The `precompressed` option checks if files with extensions like `.br` or `.gz` are available and serves them based on the `Accept-Encoding` header. It prioritizes Brotli, then Zstd, and Gzip. If none are available, it serves the original file.
```ts
app.get(
'/static/*',
serveStatic({
precompressed: true,
})
)
```
## Testing
You can use `bun:test` for testing on Bun.
```ts
import { describe, expect, it } from 'bun:test'
import app from '.'
describe('My first test', () => {
it('Should return 200 Response', async () => {
const req = new Request('http://localhost/')
const res = await app.fetch(req)
expect(res.status).toBe(200)
})
})
```
Then, run the command.
```sh
bun test index.test.ts
```
# Cloudflare Pages
[Cloudflare Pages](https://pages.cloudflare.com) is an edge platform for full-stack web applications.
It serves static files and dynamic content provided by Cloudflare Workers.
Hono fully supports Cloudflare Pages.
It introduces a delightful developer experience. Vite's dev server is fast, and deploying with Wrangler is super quick.
## 1. Setup
A starter for Cloudflare Pages is available.
Start your project with "create-hono" command.
Select `cloudflare-pages` template for this example.
::: code-group
```sh [npm]
npm create hono@latest my-app
```
```sh [yarn]
yarn create hono my-app
```
```sh [pnpm]
pnpm create hono my-app
```
```sh [bun]
bun create hono@latest my-app
```
```sh [deno]
deno init --npm hono my-app
```
:::
Move into `my-app` and install the dependencies.
::: code-group
```sh [npm]
cd my-app
npm i
```
```sh [yarn]
cd my-app
yarn
```
```sh [pnpm]
cd my-app
pnpm i
```
```sh [bun]
cd my-app
bun i
```
:::
Below is a basic directory structure.
```text
./
├── package.json
├── public
│ └── static // Put your static files.
│ └── style.css // You can refer to it as `/static/style.css`.
├── src
│ ├── index.tsx // The entry point for server-side.
│ └── renderer.tsx
├── tsconfig.json
└── vite.config.ts
```
## 2. Hello World
Edit `src/index.tsx` like the following:
```tsx
import { Hono } from 'hono'
import { renderer } from './renderer'
const app = new Hono()
app.get('*', renderer)
app.get('/', (c) => {
return c.render(
Hello, Cloudflare Pages!
)
})
export default app
```
## 3. Run
Run the development server locally. Then, access `http://localhost:5173` in your Web browser.
::: code-group
```sh [npm]
npm run dev
```
```sh [yarn]
yarn dev
```
```sh [pnpm]
pnpm dev
```
```sh [bun]
bun run dev
```
:::
## 4. Deploy
If you have a Cloudflare account, you can deploy to Cloudflare. In `package.json`, `$npm_execpath` needs to be changed to your package manager of choice.
::: code-group
```sh [npm]
npm run deploy
```
```sh [yarn]
yarn deploy
```
```sh [pnpm]
pnpm run deploy
```
```sh [bun]
bun run deploy
```
:::
### Deploy via the Cloudflare dashboard with GitHub
1. Log in to the [Cloudflare dashboard](https://dash.cloudflare.com) and select your account.
2. In Account Home, select Workers & Pages > Create application > Pages > Connect to Git.
3. Authorize your GitHub account, and select the repository. In Set up builds and deployments, provide the following information:
| Configuration option | Value |
| -------------------- | --------------- |
| Production branch | `main` |
| Build command | `npm run build` |
| Build directory | `dist` |
## Bindings
You can use Cloudflare Bindings like Variables, KV, D1, and others.
In this section, let's use Variables and KV.
### Create `wrangler.toml`
First, create `wrangler.toml` for local Bindings:
```sh
touch wrangler.toml
```
Edit `wrangler.toml`. Specify Variable with the name `MY_NAME`.
```toml
[vars]
MY_NAME = "Hono"
```
### Create KV
Next, make the KV. Run the following `wrangler` command:
```sh
wrangler kv namespace create MY_KV --preview
```
Note down the `preview_id` as the following output:
```
{ binding = "MY_KV", preview_id = "abcdef" }
```
Specify `preview_id` with the name of Bindings, `MY_KV`:
```toml
[[kv_namespaces]]
binding = "MY_KV"
id = "abcdef"
```
### Edit `vite.config.ts`
Edit the `vite.config.ts`:
```ts
import devServer from '@hono/vite-dev-server'
import adapter from '@hono/vite-dev-server/cloudflare'
import build from '@hono/vite-cloudflare-pages'
import { defineConfig } from 'vite'
export default defineConfig({
plugins: [
devServer({
entry: 'src/index.tsx',
adapter, // Cloudflare Adapter
}),
build(),
],
})
```
### Use Bindings in your application
Use Variable and KV in your application. Set the types.
```ts
type Bindings = {
MY_NAME: string
MY_KV: KVNamespace
}
const app = new Hono<{ Bindings: Bindings }>()
```
Use them:
```tsx
app.get('/', async (c) => {
await c.env.MY_KV.put('name', c.env.MY_NAME)
const name = await c.env.MY_KV.get('name')
return c.render(
Hello! {name}
)
})
```
### In production
For Cloudflare Pages, you will use `wrangler.toml` for local development, but for production, you will set up Bindings in the dashboard.
## Client-side
You can write client-side scripts and import them into your application using Vite's features.
If `/src/client.ts` is the entry point for the client, simply write it in the script tag.
Additionally, `import.meta.env.PROD` is useful for detecting whether it's running on a dev server or in the build phase.
```tsx
app.get('/', (c) => {
return c.html(
{import.meta.env.PROD ? (
) : (
)}
Hello
)
})
```
In order to build the script properly, you can use the example config file `vite.config.ts` as shown below.
```ts
import pages from '@hono/vite-cloudflare-pages'
import devServer from '@hono/vite-dev-server'
import { defineConfig } from 'vite'
export default defineConfig(({ mode }) => {
if (mode === 'client') {
return {
build: {
rollupOptions: {
input: './src/client.ts',
output: {
entryFileNames: 'static/client.js',
},
},
},
}
} else {
return {
plugins: [
pages(),
devServer({
entry: 'src/index.tsx',
}),
],
}
}
})
```
You can run the following command to build the server and client script.
```sh
vite build --mode client && vite build
```
## Cloudflare Pages Middleware
Cloudflare Pages uses its own [middleware](https://developers.cloudflare.com/pages/functions/middleware/) system that is different from Hono's middleware. You can enable it by exporting `onRequest` in a file named `_middleware.ts` like this:
```ts
// functions/_middleware.ts
export async function onRequest(pagesContext) {
console.log(`You are accessing ${pagesContext.request.url}`)
return await pagesContext.next()
}
```
Using `handleMiddleware`, you can use Hono's middleware as Cloudflare Pages middleware.
```ts
// functions/_middleware.ts
import { handleMiddleware } from 'hono/cloudflare-pages'
export const onRequest = handleMiddleware(async (c, next) => {
console.log(`You are accessing ${c.req.url}`)
await next()
})
```
You can also use built-in and 3rd party middleware for Hono. For example, to add Basic Authentication, you can use [Hono's Basic Authentication Middleware](/docs/middleware/builtin/basic-auth).
```ts
// functions/_middleware.ts
import { handleMiddleware } from 'hono/cloudflare-pages'
import { basicAuth } from 'hono/basic-auth'
export const onRequest = handleMiddleware(
basicAuth({
username: 'hono',
password: 'acoolproject',
})
)
```
If you want to apply multiple middleware, you can write it like this:
```ts
import { handleMiddleware } from 'hono/cloudflare-pages'
// ...
export const onRequest = [
handleMiddleware(middleware1),
handleMiddleware(middleware2),
handleMiddleware(middleware3),
]
```
### Accessing `EventContext`
You can access [`EventContext`](https://developers.cloudflare.com/pages/functions/api-reference/#eventcontext) object via `c.env` in `handleMiddleware`.
```ts
// functions/_middleware.ts
import { handleMiddleware } from 'hono/cloudflare-pages'
export const onRequest = [
handleMiddleware(async (c, next) => {
c.env.eventContext.data.user = 'Joe'
await next()
}),
]
```
Then, you can access the data value in via `c.env.eventContext` in the handler:
```ts
// functions/api/[[route]].ts
import type { EventContext } from 'hono/cloudflare-pages'
import { handle } from 'hono/cloudflare-pages'
// ...
type Env = {
Bindings: {
eventContext: EventContext
}
}
const app = new Hono()
app.get('/hello', (c) => {
return c.json({
message: `Hello, ${c.env.eventContext.data.user}!`, // 'Joe'
})
})
export const onRequest = handle(app)
```
# Cloudflare Workers
[Cloudflare Workers](https://workers.cloudflare.com) is a JavaScript edge runtime on Cloudflare CDN.
You can develop the application locally and publish it with a few commands using [Wrangler](https://developers.cloudflare.com/workers/wrangler/).
Wrangler includes trans compiler, so we can write the code with TypeScript.
Let’s make your first application for Cloudflare Workers with Hono.
## 1. Setup
A starter for Cloudflare Workers is available.
Start your project with "create-hono" command.
Select `cloudflare-workers` template for this example.
::: code-group
```sh [npm]
npm create hono@latest my-app
```
```sh [yarn]
yarn create hono my-app
```
```sh [pnpm]
pnpm create hono my-app
```
```sh [bun]
bun create hono@latest my-app
```
```sh [deno]
deno init --npm hono my-app
```
:::
Move to `my-app` and install the dependencies.
::: code-group
```sh [npm]
cd my-app
npm i
```
```sh [yarn]
cd my-app
yarn
```
```sh [pnpm]
cd my-app
pnpm i
```
```sh [bun]
cd my-app
bun i
```
:::
## 2. Hello World
Edit `src/index.ts` like below.
```ts
import { Hono } from 'hono'
const app = new Hono()
app.get('/', (c) => c.text('Hello Cloudflare Workers!'))
export default app
```
## 3. Run
Run the development server locally. Then, access `http://localhost:8787` in your web browser.
::: code-group
```sh [npm]
npm run dev
```
```sh [yarn]
yarn dev
```
```sh [pnpm]
pnpm dev
```
```sh [bun]
bun run dev
```
:::
### Change port number
If you need to change the port number you can follow the instructions here to update `wrangler.toml` / `wrangler.json` / `wrangler.jsonc` files:
[Wrangler Configuration](https://developers.cloudflare.com/workers/wrangler/configuration/#local-development-settings)
Or, you can follow the instructions here to set CLI options:
[Wrangler CLI](https://developers.cloudflare.com/workers/wrangler/commands/#dev)
## 4. Deploy
If you have a Cloudflare account, you can deploy to Cloudflare. In `package.json`, `$npm_execpath` needs to be changed to your package manager of choice.
::: code-group
```sh [npm]
npm run deploy
```
```sh [yarn]
yarn deploy
```
```sh [pnpm]
pnpm run deploy
```
```sh [bun]
bun run deploy
```
:::
That's all!
## Service Worker mode or Module Worker mode
There are two syntaxes for writing the Cloudflare Workers. _Module Worker mode_ and _Service Worker mode_. Using Hono, you can write with both syntax, but we recommend using Module Worker mode so that binding variables are localized.
```ts
// Module Worker
export default app
```
```ts
// Service Worker
app.fire()
```
## Using Hono with other event handlers
You can integrate Hono with other event handlers (such as `scheduled`) in _Module Worker mode_.
To do this, export `app.fetch` as the module's `fetch` handler, and then implement other handlers as needed:
```ts
const app = new Hono()
export default {
fetch: app.fetch,
scheduled: async (batch, env) => {},
}
```
## Serve static files
If you want to serve static files, you can use [the Static Assets feature](https://developers.cloudflare.com/workers/static-assets/) of Cloudflare Workers. Specify the directory for the files in `wrangler.toml`:
```toml
assets = { directory = "public" }
```
Then create the `public` directory and place the files there. For instance, `./public/static/hello.txt` will be served as `/static/hello.txt`.
```
.
├── package.json
├── public
│ ├── favicon.ico
│ └── static
│ └── hello.txt
├── src
│ └── index.ts
└── wrangler.toml
```
## Types
You have to install `@cloudflare/workers-types` if you want to have workers types.
::: code-group
```sh [npm]
npm i --save-dev @cloudflare/workers-types
```
```sh [yarn]
yarn add -D @cloudflare/workers-types
```
```sh [pnpm]
pnpm add -D @cloudflare/workers-types
```
```sh [bun]
bun add --dev @cloudflare/workers-types
```
:::
## Testing
For testing, we recommend using `@cloudflare/vitest-pool-workers`.
Refer to [examples](https://github.com/honojs/examples) for setting it up.
If there is the application below.
```ts
import { Hono } from 'hono'
const app = new Hono()
app.get('/', (c) => c.text('Please test me!'))
```
We can test if it returns "_200 OK_" Response with this code.
```ts
describe('Test the application', () => {
it('Should return 200 response', async () => {
const res = await app.request('http://localhost/')
expect(res.status).toBe(200)
})
})
```
## Bindings
In the Cloudflare Workers, we can bind the environment values, KV namespace, R2 bucket, or Durable Object. You can access them in `c.env`. It will have the types if you pass the "_type struct_" for the bindings to the `Hono` as generics.
```ts
type Bindings = {
MY_BUCKET: R2Bucket
USERNAME: string
PASSWORD: string
}
const app = new Hono<{ Bindings: Bindings }>()
// Access to environment values
app.put('/upload/:key', async (c, next) => {
const key = c.req.param('key')
await c.env.MY_BUCKET.put(key, c.req.body)
return c.text(`Put ${key} successfully!`)
})
```
## Using Variables in Middleware
This is the only case for Module Worker mode.
If you want to use Variables or Secret Variables in Middleware, for example, "username" or "password" in Basic Authentication Middleware, you need to write like the following.
```ts
import { basicAuth } from 'hono/basic-auth'
type Bindings = {
USERNAME: string
PASSWORD: string
}
const app = new Hono<{ Bindings: Bindings }>()
//...
app.use('/auth/*', async (c, next) => {
const auth = basicAuth({
username: c.env.USERNAME,
password: c.env.PASSWORD,
})
return auth(c, next)
})
```
The same is applied to Bearer Authentication Middleware, JWT Authentication, or others.
## Deploy from GitHub Actions
Before deploying code to Cloudflare via CI, you need a Cloudflare token. You can manage it from [User API Tokens](https://dash.cloudflare.com/profile/api-tokens).
If it's a newly created token, select the **Edit Cloudflare Workers** template, if you already have another token, make sure the token has the corresponding permissions(No, token permissions are not shared between Cloudflare Pages and Cloudflare Workers).
then go to your GitHub repository settings dashboard: `Settings->Secrets and variables->Actions->Repository secrets`, and add a new secret with the name `CLOUDFLARE_API_TOKEN`.
then create `.github/workflows/deploy.yml` in your Hono project root folder, paste the following code:
```yml
name: Deploy
on:
push:
branches:
- main
jobs:
deploy:
runs-on: ubuntu-latest
name: Deploy
steps:
- uses: actions/checkout@v4
- name: Deploy
uses: cloudflare/wrangler-action@v3
with:
apiToken: ${{ secrets.CLOUDFLARE_API_TOKEN }}
```
then edit `wrangler.toml`, and add this code after `compatibility_date` line.
```toml
main = "src/index.ts"
minify = true
```
Everything is ready! Now push the code and enjoy it.
## Load env when local development
To configure the environment variables for local development, create the `.dev.vars` file in the root directory of the project.
Then configure your environment variables as you would with a normal env file.
```
SECRET_KEY=value
API_TOKEN=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9
```
> For more about this section you can find in the Cloudflare documentation:
> https://developers.cloudflare.com/workers/wrangler/configuration/#secrets
Then we use the `c.env.*` to get the environment variables in our code.
**For Cloudflare Workers, environment variables must be obtained via `c`, not via `process.env`.**
```ts
type Bindings = {
SECRET_KEY: string
}
const app = new Hono<{ Bindings: Bindings }>()
app.get('/env', (c) => {
const SECRET_KEY = c.env.SECRET_KEY
return c.text(SECRET_KEY)
})
```
Before you deploy your project to Cloudflare, remember to set the environment variable/secrets in the Cloudflare Workers project's configuration.
> For more about this section you can find in the Cloudflare documentation:
> https://developers.cloudflare.com/workers/configuration/environment-variables/#add-environment-variables-via-the-dashboard
# Deno
[Deno](https://deno.com/) is a JavaScript runtime built on V8. It's not Node.js.
Hono also works on Deno.
You can use Hono, write the code with TypeScript, run the application with the `deno` command, and deploy it to "Deno Deploy".
## 1. Install Deno
First, install `deno` command.
Please refer to [the official document](https://docs.deno.com/runtime/manual/getting_started/installation).
## 2. Setup
A starter for Deno is available.
Start your project with "create-hono" command.
```sh
deno init --npm hono my-app
```
Select `deno` template for this example.
Move into `my-app`. For Deno, you don't have to install Hono explicitly.
```sh
cd my-app
```
## 3. Hello World
Write your first application.
```ts
import { Hono } from 'hono'
const app = new Hono()
app.get('/', (c) => c.text('Hello Deno!'))
Deno.serve(app.fetch)
```
## 4. Run
Just this command:
```sh
deno task start
```
## Change port number
You can specify the port number by updating the arguments of `Deno.serve` in `main.ts`:
```ts
Deno.serve(app.fetch) // [!code --]
Deno.serve({ port: 8787 }, app.fetch) // [!code ++]
```
## Serve static files
To serve static files, use `serveStatic` imported from `hono/middleware.ts`.
```ts
import { Hono } from 'hono'
import { serveStatic } from 'hono/deno'
const app = new Hono()
app.use('/static/*', serveStatic({ root: './' }))
app.use('/favicon.ico', serveStatic({ path: './favicon.ico' }))
app.get('/', (c) => c.text('You can access: /static/hello.txt'))
app.get('*', serveStatic({ path: './static/fallback.txt' }))
Deno.serve(app.fetch)
```
For the above code, it will work well with the following directory structure.
```
./
├── favicon.ico
├── index.ts
└── static
├── demo
│ └── index.html
├── fallback.txt
├── hello.txt
└── images
└── dinotocat.png
```
### `rewriteRequestPath`
If you want to map `http://localhost:8000/static/*` to `./statics`, you can use the `rewriteRequestPath` option:
```ts
app.get(
'/static/*',
serveStatic({
root: './',
rewriteRequestPath: (path) =>
path.replace(/^\/static/, '/statics'),
})
)
```
### `mimes`
You can add MIME types with `mimes`:
```ts
app.get(
'/static/*',
serveStatic({
mimes: {
m3u8: 'application/vnd.apple.mpegurl',
ts: 'video/mp2t',
},
})
)
```
### `onFound`
You can specify handling when the requested file is found with `onFound`:
```ts
app.get(
'/static/*',
serveStatic({
// ...
onFound: (_path, c) => {
c.header('Cache-Control', `public, immutable, max-age=31536000`)
},
})
)
```
### `onNotFound`
You can specify handling when the requested file is not found with `onNotFound`:
```ts
app.get(
'/static/*',
serveStatic({
onNotFound: (path, c) => {
console.log(`${path} is not found, you access ${c.req.path}`)
},
})
)
```
### `precompressed`
The `precompressed` option checks if files with extensions like `.br` or `.gz` are available and serves them based on the `Accept-Encoding` header. It prioritizes Brotli, then Zstd, and Gzip. If none are available, it serves the original file.
```ts
app.get(
'/static/*',
serveStatic({
precompressed: true,
})
)
```
## Deno Deploy
Deno Deploy is an edge runtime platform for Deno.
We can publish the application world widely on Deno Deploy.
Hono also supports Deno Deploy. Please refer to [the official document](https://docs.deno.com/deploy/manual/).
## Testing
Testing the application on Deno is easy.
You can write with `Deno.test` and use `assert` or `assertEquals` from [@std/assert](https://jsr.io/@std/assert).
```sh
deno add jsr:@std/assert
```
```ts
import { Hono } from 'hono'
import { assertEquals } from '@std/assert'
Deno.test('Hello World', async () => {
const app = new Hono()
app.get('/', (c) => c.text('Please test me'))
const res = await app.request('http://localhost/')
assertEquals(res.status, 200)
})
```
Then run the command:
```sh
deno test hello.ts
```
## `npm:` specifier
`npm:hono` is also available. You can use it by fixing the `deno.json`:
```json
{
"imports": {
"hono": "jsr:@hono/hono" // [!code --]
"hono": "npm:hono" // [!code ++]
}
}
```
You can use either `npm:hono` or `jsr:@hono/hono`.
If you want to use Third-party Middleware such as `npm:@hono/zod-validator` with the TypeScript Type inferences, you need to use the `npm:` specifier.
```json
{
"imports": {
"hono": "npm:hono",
"zod": "npm:zod",
"@hono/zod-validator": "npm:@hono/zod-validator"
}
}
```
# Fastly Compute
[Fastly's Compute](https://www.fastly.com/products/edge-compute) offering allows us to build high scale, globally distributed applications and execute code at the edge of Fastly CDN.
Hono also works on Fastly Compute.
## 1. Install CLI
To use Fastly Compute, you must [create a Fastly account](https://www.fastly.com/signup/) if you don't already have one.
Then, install [Fastly CLI](https://github.com/fastly/cli).
macOS
```sh
brew install fastly/tap/fastly
```
Follow this link for other OS:
- [Compute services | Fastly Developer Hub](https://developer.fastly.com/learning/compute/#download-and-install-the-fastly-cli)
## 2. Setup
A starter for Fastly Compute is available.
Start your project with "create-hono" command.
Select `fastly` template for this example.
::: code-group
```sh [npm]
npm create hono@latest my-app
```
```sh [yarn]
yarn create hono my-app
```
```sh [pnpm]
pnpm create hono my-app
```
```sh [bun]
bun create hono@latest my-app
```
```sh [deno]
deno init --npm hono my-app
```
:::
Move to `my-app` and install the dependencies.
::: code-group
```sh [npm]
cd my-app
npm i
```
```sh [yarn]
cd my-app
yarn
```
```sh [pnpm]
cd my-app
pnpm i
```
```sh [bun]
cd my-app
bun i
```
:::
## 3. Hello World
Edit `src/index.ts`:
```ts
// src/index.ts
import { Hono } from 'hono'
const app = new Hono()
app.get('/', (c) => c.text('Hello Fastly!'))
app.fire()
```
## 4. Run
Run the development server locally. Then, access `http://localhost:7676` in your Web browser.
::: code-group
```sh [npm]
npm run dev
```
```sh [yarn]
yarn dev
```
```sh [pnpm]
pnpm dev
```
```sh [bun]
bun run dev
```
:::
## 4. Deploy
::: code-group
```sh [npm]
npm run deploy
```
```sh [yarn]
yarn deploy
```
```sh [pnpm]
pnpm deploy
```
```sh [bun]
bun run deploy
```
:::
That's all!!
# Lambda@Edge
[Lambda@Edge](https://aws.amazon.com/lambda/edge/) is a serverless platform by Amazon Web Services. It allows you to run Lambda functions at Amazon CloudFront's edge locations, enabling you to customize behaviors for HTTP requests/responses.
Hono supports Lambda@Edge with the Node.js 18+ environment.
## 1. Setup
When creating the application on Lambda@Edge,
[CDK](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-cdk.html)
is useful to setup the functions such as CloudFront, IAM Role, API Gateway, and others.
Initialize your project with the `cdk` CLI.
::: code-group
```sh [npm]
mkdir my-app
cd my-app
cdk init app -l typescript
npm i hono
mkdir lambda
```
```sh [yarn]
mkdir my-app
cd my-app
cdk init app -l typescript
yarn add hono
mkdir lambda
```
```sh [pnpm]
mkdir my-app
cd my-app
cdk init app -l typescript
pnpm add hono
mkdir lambda
```
```sh [bun]
mkdir my-app
cd my-app
cdk init app -l typescript
bun add hono
mkdir lambda
```
:::
## 2. Hello World
Edit `lambda/index_edge.ts`.
```ts
import { Hono } from 'hono'
import { handle } from 'hono/lambda-edge'
const app = new Hono()
app.get('/', (c) => c.text('Hello Hono on Lambda@Edge!'))
export const handler = handle(app)
```
## 3. Deploy
Edit `bin/my-app.ts`.
```ts
#!/usr/bin/env node
import 'source-map-support/register'
import * as cdk from 'aws-cdk-lib'
import { MyAppStack } from '../lib/my-app-stack'
const app = new cdk.App()
new MyAppStack(app, 'MyAppStack', {
env: {
account: process.env.CDK_DEFAULT_ACCOUNT,
region: 'us-east-1',
},
})
```
Edit `lambda/cdk-stack.ts`.
```ts
import { Construct } from 'constructs'
import * as cdk from 'aws-cdk-lib'
import * as cloudfront from 'aws-cdk-lib/aws-cloudfront'
import * as origins from 'aws-cdk-lib/aws-cloudfront-origins'
import * as lambda from 'aws-cdk-lib/aws-lambda'
import { NodejsFunction } from 'aws-cdk-lib/aws-lambda-nodejs'
import * as s3 from 'aws-cdk-lib/aws-s3'
export class MyAppStack extends cdk.Stack {
public readonly edgeFn: lambda.Function
constructor(scope: Construct, id: string, props?: cdk.StackProps) {
super(scope, id, props)
const edgeFn = new NodejsFunction(this, 'edgeViewer', {
entry: 'lambda/index_edge.ts',
handler: 'handler',
runtime: lambda.Runtime.NODEJS_20_X,
})
// Upload any html
const originBucket = new s3.Bucket(this, 'originBucket')
new cloudfront.Distribution(this, 'Cdn', {
defaultBehavior: {
origin: new origins.S3Origin(originBucket),
edgeLambdas: [
{
functionVersion: edgeFn.currentVersion,
eventType: cloudfront.LambdaEdgeEventType.VIEWER_REQUEST,
},
],
},
})
}
}
```
Finally, run the command to deploy:
```sh
cdk deploy
```
## Callback
If you want to add Basic Auth and continue with request processing after verification, you can use `c.env.callback()`
```ts
import { Hono } from 'hono'
import { basicAuth } from 'hono/basic-auth'
import type { Callback, CloudFrontRequest } from 'hono/lambda-edge'
import { handle } from 'hono/lambda-edge'
type Bindings = {
callback: Callback
request: CloudFrontRequest
}
const app = new Hono<{ Bindings: Bindings }>()
app.get(
'*',
basicAuth({
username: 'hono',
password: 'acoolproject',
})
)
app.get('/', async (c, next) => {
await next()
c.env.callback(null, c.env.request)
})
export const handler = handle(app)
```
# Netlify
Netlify provides static site hosting and serverless backend services. [Edge Functions](https://docs.netlify.com/edge-functions/overview/) enables us to make the web pages dynamic.
Edge Functions support writing in Deno and TypeScript, and deployment is made easy through the [Netlify CLI](https://docs.netlify.com/cli/get-started/). With Hono, you can create the application for Netlify Edge Functions.
## 1. Setup
A starter for Netlify is available.
Start your project with "create-hono" command.
Select `netlify` template for this example.
::: code-group
```sh [npm]
npm create hono@latest my-app
```
```sh [yarn]
yarn create hono my-app
```
```sh [pnpm]
pnpm create hono my-app
```
```sh [bun]
bun create hono@latest my-app
```
```sh [deno]
deno init --npm hono my-app
```
:::
Move into `my-app`.
## 2. Hello World
Edit `netlify/edge-functions/index.ts`:
```ts
import { Hono } from 'jsr:@hono/hono'
import { handle } from 'jsr:@hono/hono/netlify'
const app = new Hono()
app.get('/', (c) => {
return c.text('Hello Hono!')
})
export default handle(app)
```
## 3. Run
Run the development server with Netlify CLI. Then, access `http://localhost:8888` in your Web browser.
```sh
netlify dev
```
## 4. Deploy
You can deploy with a `netlify deploy` command.
```sh
netlify deploy --prod
```
## `Context`
You can access the Netlify's `Context` through `c.env`:
```ts
import { Hono } from 'jsr:@hono/hono'
import { handle } from 'jsr:@hono/hono/netlify'
// Import the type definition
import type { Context } from 'https://edge.netlify.com/'
export type Env = {
Bindings: {
context: Context
}
}
const app = new Hono()
app.get('/country', (c) =>
c.json({
'You are in': c.env.context.geo.country?.name,
})
)
export default handle(app)
```
# Node.js
[Node.js](https://nodejs.org/) is an open-source, cross-platform JavaScript runtime environment.
Hono was not designed for Node.js at first. But with a [Node.js Adapter](https://github.com/honojs/node-server) it can run on Node.js as well.
::: info
It works on Node.js versions greater than 18.x. The specific required Node.js versions are as follows:
- 18.x => 18.14.1+
- 19.x => 19.7.0+
- 20.x => 20.0.0+
Essentially, you can simply use the latest version of each major release.
:::
## 1. Setup
A starter for Node.js is available.
Start your project with "create-hono" command.
Select `nodejs` template for this example.
::: code-group
```sh [npm]
npm create hono@latest my-app
```
```sh [yarn]
yarn create hono my-app
```
```sh [pnpm]
pnpm create hono my-app
```
```sh [bun]
bun create hono@latest my-app
```
```sh [deno]
deno init --npm hono my-app
```
:::
Move to `my-app` and install the dependencies.
::: code-group
```sh [npm]
cd my-app
npm i
```
```sh [yarn]
cd my-app
yarn
```
```sh [pnpm]
cd my-app
pnpm i
```
```sh [bun]
cd my-app
bun i
```
:::
## 2. Hello World
Edit `src/index.ts`:
```ts
import { serve } from '@hono/node-server'
import { Hono } from 'hono'
const app = new Hono()
app.get('/', (c) => c.text('Hello Node.js!'))
serve(app)
```
## 3. Run
Run the development server locally. Then, access `http://localhost:3000` in your Web browser.
::: code-group
```sh [npm]
npm run dev
```
```sh [yarn]
yarn dev
```
```sh [pnpm]
pnpm dev
```
:::
## Change port number
You can specify the port number with the `port` option.
```ts
serve({
fetch: app.fetch,
port: 8787,
})
```
## Access the raw Node.js APIs
You can access the Node.js APIs from `c.env.incoming` and `c.env.outgoing`.
```ts
import { Hono } from 'hono'
import { serve, type HttpBindings } from '@hono/node-server'
// or `Http2Bindings` if you use HTTP2
type Bindings = HttpBindings & {
/* ... */
}
const app = new Hono<{ Bindings: Bindings }>()
app.get('/', (c) => {
return c.json({
remoteAddress: c.env.incoming.socket.remoteAddress,
})
})
serve(app)
```
## Serve static files
You can use `serveStatic` to serve static files from the local file system. For example, suppose the directory structure is as follows:
```sh
./
├── favicon.ico
├── index.ts
└── static
├── hello.txt
└── image.png
```
If access to the path `/static/*` comes in and returns a file under `./static`, you can write the following:
```ts
import { serveStatic } from '@hono/node-server/serve-static'
app.use('/static/*', serveStatic({ root: './' }))
```
Use the `path` option to serve `favicon.ico` in the directory root:
```ts
app.use('/favicon.ico', serveStatic({ path: './favicon.ico' }))
```
If access comes to the path `/hello.txt` or `/image.png` and returns a file named `./static/hello.txt` or `./static/image.png`, you can use the following:
```ts
app.use('*', serveStatic({ root: './static' }))
```
### `rewriteRequestPath`
If you want to map `http://localhost:3000/static/*` to `./statics`, you can use the `rewriteRequestPath` option:
```ts
app.get(
'/static/*',
serveStatic({
root: './',
rewriteRequestPath: (path) =>
path.replace(/^\/static/, '/statics'),
})
)
```
## http2
You can run hono on a [Node.js http2 Server](https://nodejs.org/api/http2.html).
### unencrypted http2
```ts
import { createServer } from 'node:http2'
const server = serve({
fetch: app.fetch,
createServer,
})
```
### encrypted http2
```ts
import { createSecureServer } from 'node:http2'
import { readFileSync } from 'node:fs'
const server = serve({
fetch: app.fetch,
createServer: createSecureServer,
serverOptions: {
key: readFileSync('localhost-privkey.pem'),
cert: readFileSync('localhost-cert.pem'),
},
})
```
## Dockerfile
Here is an example of a Dockerfile.
```Dockerfile
FROM node:20-alpine AS base
FROM base AS builder
RUN apk add --no-cache gcompat
WORKDIR /app
COPY package*json tsconfig.json src ./
RUN npm ci && \
npm run build && \
npm prune --production
FROM base AS runner
WORKDIR /app
RUN addgroup --system --gid 1001 nodejs
RUN adduser --system --uid 1001 hono
COPY --from=builder --chown=hono:nodejs /app/node_modules /app/node_modules
COPY --from=builder --chown=hono:nodejs /app/dist /app/dist
COPY --from=builder --chown=hono:nodejs /app/package.json /app/package.json
USER hono
EXPOSE 3000
CMD ["node", "/app/dist/index.js"]
```
The following steps shall be taken in advance.
1. Add `"outDir": "./dist"` to the `compilerOptions` section `tsconfig.json`.
2. Add `"exclude": ["node_modules"]` to `tsconfig.json`.
3. Add `"build": "tsc"` to `script` section of `package.json`.
4. Run `npm install typescript --save-dev`.
5. Add `"type": "module"` to `package.json`.
# Service Worker
[Service Worker](https://developer.mozilla.org/en-US/docs/Web/API/Service_Worker_API) is a script that runs in the background of the browser to handle tasks like caching and push notifications. Using a Service Worker adapter, you can run applications made with Hono as [FetchEvent](https://developer.mozilla.org/en-US/docs/Web/API/FetchEvent) handler within the browser.
This page shows an example of creating a project using [Vite](https://vitejs.dev/).
## 1. Setup
First, create and move to your project directory:
```sh
mkdir my-app
cd my-app
```
Create the necessary files for the project. Make a `package.json` file with the following:
```json
{
"name": "my-app",
"private": true,
"scripts": {
"dev": "vite dev"
},
"type": "module"
}
```
Similarly, create a `tsconfig.json` file with the following:
```json
{
"compilerOptions": {
"target": "ES2020",
"module": "ESNext",
"lib": ["ES2020", "DOM", "WebWorker"],
"moduleResolution": "bundler"
},
"include": ["./"],
"exclude": ["node_modules"]
}
```
Next, install the necessary modules.
::: code-group
```sh [npm]
npm i hono
npm i -D vite
```
```sh [yarn]
yarn add hono
yarn add -D vite
```
```sh [pnpm]
pnpm add hono
pnpm add -D vite
```
```sh [bun]
bun add hono
bun add -D vite
```
:::
## 2. Hello World
Edit `index.html`:
```html
Hello World by Service Worker
```
`main.ts` is a script to register the Service Worker:
```ts
function register() {
navigator.serviceWorker
.register('/sw.ts', { scope: '/sw', type: 'module' })
.then(
function (_registration) {
console.log('Register Service Worker: Success')
},
function (_error) {
console.log('Register Service Worker: Error')
}
)
}
function start() {
navigator.serviceWorker
.getRegistrations()
.then(function (registrations) {
for (const registration of registrations) {
console.log('Unregister Service Worker')
registration.unregister()
}
register()
})
}
start()
```
In `sw.ts`, create an application using Hono and register it to the `fetch` event with the Service Worker adapter’s `handle` function. This allows the Hono application to intercept access to `/sw`.
```ts
// To support types
// https://github.com/microsoft/TypeScript/issues/14877
declare const self: ServiceWorkerGlobalScope
import { Hono } from 'hono'
import { handle } from 'hono/service-worker'
const app = new Hono().basePath('/sw')
app.get('/', (c) => c.text('Hello World'))
self.addEventListener('fetch', handle(app))
```
## 3. Run
Start the development server.
::: code-group
```sh [npm]
npm run dev
```
```sh [yarn]
yarn dev
```
```sh [pnpm]
pnpm run dev
```
```sh [bun]
bun run dev
```
:::
By default, the development server will run on port `5173`. Access `http://localhost:5173/` in your browser to complete the Service Worker registration. Then, access `/sw` to see the response from the Hono application.
# Supabase Edge Functions
[Supabase](https://supabase.com/) is an open-source alternative to Firebase, offering a suite of tools similar to Firebase's capabilities, including database, authentication, storage, and now, serverless functions.
Supabase Edge Functions are server-side TypeScript functions that are distributed globally, running closer to your users for improved performance. These functions are developed using [Deno](https://deno.com/), which brings several benefits, including improved security and a modern JavaScript/TypeScript runtime.
Here's how you can get started with Supabase Edge Functions:
## 1. Setup
### Prerequisites
Before you begin, make sure you have the Supabase CLI installed. If you haven't installed it yet, follow the instructions in the [official documentation](https://supabase.com/docs/guides/cli/getting-started).
### Creating a New Project
1. Open your terminal or command prompt.
2. Create a new Supabase project in a directory on your local machine by running:
```bash
supabase init
```
This command initializes a new Supabase project in the current directory.
### Adding an Edge Function
3. Inside your Supabase project, create a new Edge Function named `hello-world`:
```bash
supabase functions new hello-world
```
This command creates a new Edge Function with the specified name in your project.
## 2. Hello World
Edit the `hello-world` function by modifying the file `supabase/functions/hello-world/index.ts`:
```ts
import { Hono } from 'jsr:@hono/hono'
// change this to your function name
const functionName = 'hello-world'
const app = new Hono().basePath(`/${functionName}`)
app.get('/hello', (c) => c.text('Hello from hono-server!'))
Deno.serve(app.fetch)
```
## 3. Run
To run the function locally, use the following command:
1. Use the following command to serve the function:
```bash
supabase start # start the supabase stack
supabase functions serve --no-verify-jwt # start the Functions watcher
```
The `--no-verify-jwt` flag allows you to bypass JWT verification during local development.
2. Make a GET request using cURL or Postman to `http://127.0.0.1:54321/functions/v1/hello-world/hello`:
```bash
curl --location 'http://127.0.0.1:54321/functions/v1/hello-world/hello'
```
This request should return the text "Hello from hono-server!".
## 4. Deploy
You can deploy all of your Edge Functions in Supabase with a single command:
```bash
supabase functions deploy
```
Alternatively, you can deploy individual Edge Functions by specifying the name of the function in the deploy command:
```bash
supabase functions deploy hello-world
```
For more deployment methods, visit the Supabase documentation on [Deploying to Production](https://supabase.com/docs/guides/functions/deploy).
# Vercel
Vercel is the platform for frontend developers, providing the speed and reliability innovators need to create at the moment of inspiration. This section introduces Next.js running on Vercel.
Next.js is a flexible React framework that gives you building blocks to create fast web applications.
In Next.js, [Edge Functions](https://vercel.com/docs/concepts/functions/edge-functions) allows you to create dynamic APIs on Edge Runtime such as Vercel.
With Hono, you can write APIs with the same syntax as other runtimes and use many middleware.
## 1. Setup
A starter for Next.js is available.
Start your project with "create-hono" command.
Select `nextjs` template for this example.
::: code-group
```sh [npm]
npm create hono@latest my-app
```
```sh [yarn]
yarn create hono my-app
```
```sh [pnpm]
pnpm create hono my-app
```
```sh [bun]
bun create hono@latest my-app
```
```sh [deno]
deno init --npm hono my-app
```
:::
Move into `my-app` and install the dependencies.
::: code-group
```sh [npm]
cd my-app
npm i
```
```sh [yarn]
cd my-app
yarn
```
```sh [pnpm]
cd my-app
pnpm i
```
```sh [bun]
cd my-app
bun i
```
:::
## 2. Hello World
If you use the App Router, Edit `app/api/[[...route]]/route.ts`. Refer to the [Supported HTTP Methods](https://nextjs.org/docs/app/building-your-application/routing/route-handlers#supported-http-methods) section for more options.
```ts
import { Hono } from 'hono'
import { handle } from 'hono/vercel'
export const runtime = 'edge'
const app = new Hono().basePath('/api')
app.get('/hello', (c) => {
return c.json({
message: 'Hello Next.js!',
})
})
export const GET = handle(app)
export const POST = handle(app)
```
If you use the Pages Router, Edit `pages/api/[[...route]].ts`.
```ts
import { Hono } from 'hono'
import { handle } from 'hono/vercel'
import type { PageConfig } from 'next'
export const config: PageConfig = {
runtime: 'edge',
}
const app = new Hono().basePath('/api')
app.get('/hello', (c) => {
return c.json({
message: 'Hello Next.js!',
})
})
export default handle(app)
```
## 3. Run
Run the development server locally. Then, access `http://localhost:3000` in your Web browser.
::: code-group
```sh [npm]
npm run dev
```
```sh [yarn]
yarn dev
```
```sh [pnpm]
pnpm dev
```
```sh [bun]
bun run dev
```
:::
Now, `/api/hello` just returns JSON, but if you build React UIs, you can create a full-stack application with Hono.
## 4. Deploy
If you have a Vercel account, you can deploy by linking the Git repository.
## Node.js
You can also run Hono on Next.js running on the Node.js runtime.
### App Router
For the App Router, you can simply set the runtime to `nodejs` in your route handler:
```ts
import { Hono } from 'hono'
import { handle } from 'hono/vercel'
export const runtime = 'nodejs'
const app = new Hono().basePath('/api')
app.get('/hello', (c) => {
return c.json({
message: 'Hello from Hono!',
})
})
export const GET = handle(app)
export const POST = handle(app)
```
### Pages Router
For the Pages Router, you'll need to install the Node.js adapter first:
::: code-group
```sh [npm]
npm i @hono/node-server
```
```sh [yarn]
yarn add @hono/node-server
```
```sh [pnpm]
pnpm add @hono/node-server
```
```sh [bun]
bun add @hono/node-server
```
:::
Then, you can utilize the `handle` function imported from `@hono/node-server/vercel`:
```ts
import { Hono } from 'hono'
import { handle } from '@hono/node-server/vercel'
import type { PageConfig } from 'next'
export const config: PageConfig = {
api: {
bodyParser: false,
},
}
const app = new Hono().basePath('/api')
app.get('/hello', (c) => {
return c.json({
message: 'Hello from Hono!',
})
})
export default handle(app)
```
In order for this to work with the Pages Router, it's important to disable Vercel Node.js helpers by setting up an environment variable in your project dashboard or in your `.env` file:
```text
NODEJS_HELPERS=0
```
# Benchmarks
Benchmarks are only benchmarks, but they are important to us.
## Routers
We measured the speeds of a bunch of JavaScript routers.
For example, `find-my-way` is a very fast router used inside Fastify.
- @medley/router
- find-my-way
- koa-tree-router
- trek-router
- express (includes handling)
- koa-router
First, we registered the following routing to each of our routers.
These are similar to those used in the real world.
```ts twoslash
interface Route {
method: string
path: string
}
// ---cut---
export const routes: Route[] = [
{ method: 'GET', path: '/user' },
{ method: 'GET', path: '/user/comments' },
{ method: 'GET', path: '/user/avatar' },
{ method: 'GET', path: '/user/lookup/username/:username' },
{ method: 'GET', path: '/user/lookup/email/:address' },
{ method: 'GET', path: '/event/:id' },
{ method: 'GET', path: '/event/:id/comments' },
{ method: 'POST', path: '/event/:id/comment' },
{ method: 'GET', path: '/map/:location/events' },
{ method: 'GET', path: '/status' },
{ method: 'GET', path: '/very/deeply/nested/route/hello/there' },
{ method: 'GET', path: '/static/*' },
]
```
Then we sent the Request to the endpoints like below.
```ts twoslash
interface Route {
method: string
path: string
}
// ---cut---
const routes: (Route & { name: string })[] = [
{
name: 'short static',
method: 'GET',
path: '/user',
},
{
name: 'static with same radix',
method: 'GET',
path: '/user/comments',
},
{
name: 'dynamic route',
method: 'GET',
path: '/user/lookup/username/hey',
},
{
name: 'mixed static dynamic',
method: 'GET',
path: '/event/abcd1234/comments',
},
{
name: 'post',
method: 'POST',
path: '/event/abcd1234/comment',
},
{
name: 'long static',
method: 'GET',
path: '/very/deeply/nested/route/hello/there',
},
{
name: 'wildcard',
method: 'GET',
path: '/static/index.html',
},
]
```
Let's see the results.
### On Node.js
The following screenshots show the results on Node.js.
### On Bun
The following screenshots show the results on Bun.
## Cloudflare Workers
**Hono is the fastest**, compared to other routers for Cloudflare Workers.
- Machine: Apple MacBook Pro, 32 GiB, M1 Pro
- Scripts: [benchmarks/handle-event](https://github.com/honojs/hono/tree/main/benchmarks/handle-event)
```
Hono x 402,820 ops/sec ±4.78% (80 runs sampled)
itty-router x 212,598 ops/sec ±3.11% (87 runs sampled)
sunder x 297,036 ops/sec ±4.76% (77 runs sampled)
worktop x 197,345 ops/sec ±2.40% (88 runs sampled)
Fastest is Hono
✨ Done in 28.06s.
```
## Deno
**Hono is the fastest**, compared to other frameworks for Deno.
- Machine: Apple MacBook Pro, 32 GiB, M1 Pro, Deno v1.22.0
- Scripts: [benchmarks/deno](https://github.com/honojs/hono/tree/main/benchmarks/deno)
- Method: `bombardier --fasthttp -d 10s -c 100 'http://localhost:8000/user/lookup/username/foo'`
| Framework | Version | Results |
| --------- | :----------: | -----------------------: |
| **Hono** | 3.0.0 | **Requests/sec: 136112** |
| Fast | 4.0.0-beta.1 | Requests/sec: 103214 |
| Megalo | 0.3.0 | Requests/sec: 64597 |
| Faster | 5.7 | Requests/sec: 54801 |
| oak | 10.5.1 | Requests/sec: 43326 |
| opine | 2.2.0 | Requests/sec: 30700 |
Another benchmark result: [denosaurs/bench](https://github.com/denosaurs/bench)
## Bun
Hono is one of the fastest frameworks for Bun.
You can see it below.
- [SaltyAom/bun-http-framework-benchmark](https://github.com/SaltyAom/bun-http-framework-benchmark)
# Developer Experience
To create a great application, we need great development experience.
Fortunately, we can write applications for Cloudflare Workers, Deno, and Bun in TypeScript without having the transpiling to JavaScript.
Hono is written in TypeScript and can make applications Type-safe.
# Middleware
We call the primitive that returns `Response` as "Handler".
"Middleware" is executed before and after the Handler and handles the `Request` and `Response`.
It's like an onion structure.
For example, we can write the middleware to add the "X-Response-Time" header as follows.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.use(async (c, next) => {
const start = Date.now()
await next()
const end = Date.now()
c.res.headers.set('X-Response-Time', `${end - start}`)
})
```
With this simple method, we can write our own custom middleware and we can use the built-in or third party middleware.
# Philosophy
In this section, we talk about the concept, or philosophy, of Hono.
## Motivation
At first, I just wanted to create a web application on Cloudflare Workers.
But, there was no good framework that works on Cloudflare Workers.
So, I started building Hono.
I thought it would be a good opportunity to learn how to build a router using Trie trees.
Then a friend showed up with ultra crazy fast router called "RegExpRouter".
And I also have a friend who created the Basic authentication middleware.
Using only Web Standard APIs, we could make it work on Deno and Bun. When people asked "is there Express for Bun?", we could answer, "no, but there is Hono".
(Although Express works on Bun now.)
We also have friends who make GraphQL servers, Firebase authentication, and Sentry middleware.
And, we also have a Node.js adapter.
An ecosystem has sprung up.
In other words, Hono is damn fast, makes a lot of things possible, and works anywhere.
We might imagine that Hono could become the **Standard for Web Standards**.
# Routers
The routers are the most important features for Hono.
Hono has five routers.
## RegExpRouter
**RegExpRouter** is the fastest router in the JavaScript world.
Although this is called "RegExp" it is not an Express-like implementation using [path-to-regexp](https://github.com/pillarjs/path-to-regexp).
They are using linear loops.
Therefore, regular expression matching will be performed for all routes and the performance will be degraded as you have more routes.
Hono's RegExpRouter turns the route pattern into "one large regular expression".
Then it can get the result with one-time matching.
This works faster than methods that use tree-based algorithms such as radix-tree in most cases.
## TrieRouter
**TrieRouter** is the router using the Trie-tree algorithm.
It does not use linear loops as same as RegExpRouter.
This router is not as fast as the RegExpRouter, but it is much faster than the Express router.
TrieRouter supports all patterns though RegExpRouter does not.
## SmartRouter
RegExpRouter doesn't support all routing patterns.
Therefore, it's usually used in combination with another router that does support all patterns.
**SmartRouter** will select the best router by inferring from the registered routers.
Hono uses SmartRouter and the two routers by default:
```ts
// Inside the core of Hono.
readonly defaultRouter: Router = new SmartRouter({
routers: [new RegExpRouter(), new TrieRouter()],
})
```
When the application starts, SmartRouter detects the fastest router based on routing and continues to use it.
## LinearRouter
RegExpRouter is fast, but the route registration phase can be slightly slow.
So, it's not suitable for an environment that initializes with every request.
**LinearRouter** is optimized for "one shot" situations.
Route registration is significantly faster than with RegExpRouter because it adds the route without compiling strings, using a linear approach.
The following is one of the benchmark results, which includes the route registration phase.
```console
• GET /user/lookup/username/hey
----------------------------------------------------- -----------------------------
LinearRouter 1.82 µs/iter (1.7 µs … 2.04 µs) 1.84 µs 2.04 µs 2.04 µs
MedleyRouter 4.44 µs/iter (4.34 µs … 4.54 µs) 4.48 µs 4.54 µs 4.54 µs
FindMyWay 60.36 µs/iter (45.5 µs … 1.9 ms) 59.88 µs 78.13 µs 82.92 µs
KoaTreeRouter 3.81 µs/iter (3.73 µs … 3.87 µs) 3.84 µs 3.87 µs 3.87 µs
TrekRouter 5.84 µs/iter (5.75 µs … 6.04 µs) 5.86 µs 6.04 µs 6.04 µs
summary for GET /user/lookup/username/hey
LinearRouter
2.1x faster than KoaTreeRouter
2.45x faster than MedleyRouter
3.21x faster than TrekRouter
33.24x faster than FindMyWay
```
For situations like Fastly Compute, it's better to use LinearRouter with the `hono/quick` preset.
## PatternRouter
**PatternRouter** is the smallest router among Hono's routers.
While Hono is already compact, if you need to make it even smaller for an environment with limited resources, you can use PatternRouter.
An application using only PatternRouter is under 15KB in size.
```console
$ npx wrangler deploy --minify ./src/index.ts
⛅️ wrangler 3.20.0
-------------------
Total Upload: 14.68 KiB / gzip: 5.38 KiB
```
# Hono Stacks
Hono makes easy things easy and hard things easy.
It is suitable for not just only returning JSON.
But it's also great for building the full-stack application including REST API servers and the client.
## RPC
Hono's RPC feature allows you to share API specs with little change to your code.
The client generated by `hc` will read the spec and access the endpoint Type-Safety.
The following libraries make it possible.
- Hono - API Server
- [Zod](https://zod.dev) - Validator
- [Zod Validator Middleware](https://github.com/honojs/middleware/tree/main/packages/zod-validator)
- `hc` - HTTP Client
We can call the set of these components the **Hono Stack**.
Now let's create an API server and a client with it.
## Writing API
First, write an endpoint that receives a GET request and returns JSON.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
app.get('/hello', (c) => {
return c.json({
message: `Hello!`,
})
})
```
## Validation with Zod
Validate with Zod to receive the value of the query parameter.
```ts
import { zValidator } from '@hono/zod-validator'
import { z } from 'zod'
app.get(
'/hello',
zValidator(
'query',
z.object({
name: z.string(),
})
),
(c) => {
const { name } = c.req.valid('query')
return c.json({
message: `Hello! ${name}`,
})
}
)
```
## Sharing the Types
To emit an endpoint specification, export its type.
```ts{1,17}
const route = app.get(
'/hello',
zValidator(
'query',
z.object({
name: z.string(),
})
),
(c) => {
const { name } = c.req.valid('query')
return c.json({
message: `Hello! ${name}`,
})
}
)
export type AppType = typeof route
```
## Client
Next. The client-side implementation.
Create a client object by passing the AppType type to `hc` as generics.
Then, magically, completion works and the endpoint path and request type are suggested.
```ts
import { AppType } from './server'
import { hc } from 'hono/client'
const client = hc('/api')
const res = await client.hello.$get({
query: {
name: 'Hono',
},
})
```
The `Response` is compatible with the fetch API, but the data that can be retrieved with `json()` has a type.
```ts
const data = await res.json()
console.log(`${data.message}`)
```
Sharing API specifications means that you can be aware of server-side changes.
## With React
You can create applications on Cloudflare Pages using React.
The API server.
```ts
// functions/api/[[route]].ts
import { Hono } from 'hono'
import { handle } from 'hono/cloudflare-pages'
import { z } from 'zod'
import { zValidator } from '@hono/zod-validator'
const app = new Hono()
const schema = z.object({
id: z.string(),
title: z.string(),
})
type Todo = z.infer
const todos: Todo[] = []
const route = app
.post('/todo', zValidator('form', schema), (c) => {
const todo = c.req.valid('form')
todos.push(todo)
return c.json({
message: 'created!',
})
})
.get((c) => {
return c.json({
todos,
})
})
export type AppType = typeof route
export const onRequest = handle(app, '/api')
```
The client with React and React Query.
```tsx
// src/App.tsx
import {
useQuery,
useMutation,
QueryClient,
QueryClientProvider,
} from '@tanstack/react-query'
import { AppType } from '../functions/api/[[route]]'
import { hc, InferResponseType, InferRequestType } from 'hono/client'
const queryClient = new QueryClient()
const client = hc('/api')
export default function App() {
return (
)
}
const Todos = () => {
const query = useQuery({
queryKey: ['todos'],
queryFn: async () => {
const res = await client.todo.$get()
return await res.json()
},
})
const $post = client.todo.$post
const mutation = useMutation<
InferResponseType,
Error,
InferRequestType['form']
>(
async (todo) => {
const res = await $post({
form: todo,
})
return await res.json()
},
{
onSuccess: async () => {
queryClient.invalidateQueries({ queryKey: ['todos'] })
},
onError: (error) => {
console.log(error)
},
}
)
return (
{query.data?.todos.map((todo) => (
{todo.title}
))}
)
}
```
# Web Standards
Hono uses only **Web Standards** like Fetch.
They were originally used in the `fetch` function and consist of basic objects that handle HTTP requests and responses.
In addition to `Requests` and `Responses`, there are `URL`, `URLSearchParam`, `Headers` and others.
Cloudflare Workers, Deno, and Bun also build upon Web Standards.
For example, a server that returns "Hello World" could be written as below. This could run on Cloudflare Workers and Bun.
```ts twoslash
export default {
async fetch() {
return new Response('Hello World')
},
}
```
Hono uses only Web Standards, which means that Hono can run on any runtime that supports them.
In addition, we have a Node.js adapter. Hono runs on these runtimes:
- Cloudflare Workers (`workerd`)
- Deno
- Bun
- Fastly Compute
- AWS Lambda
- Node.js
- Vercel (edge-light)
It also works on Netlify and other platforms.
The same code runs on all platforms.
Cloudflare Workers, Deno, Shopify, and others launched [WinterCG](https://wintercg.org) to discuss the possibility of using the Web Standards to enable "web-interoperability".
Hono will follow their steps and go for **the Standard of the Web Standards**.
# Context
To handle Request and Response, you can use `Context` object.
## req
`req` is the instance of HonoRequest. For more details, see [HonoRequest](/docs/api/request).
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/hello', (c) => {
const userAgent = c.req.header('User-Agent')
// ...
// ---cut-start---
return c.text(`Hello, ${userAgent}`)
// ---cut-end---
})
```
## body()
Return the HTTP response.
You can set headers with `c.header()` and set HTTP status code with `c.status`.
This can also be set in `c.text()`, `c.json()` and so on.
::: info
**Note**: When returning Text or HTML, it is recommended to use `c.text()` or `c.html()`.
:::
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/welcome', (c) => {
// Set headers
c.header('X-Message', 'Hello!')
c.header('Content-Type', 'text/plain')
// Set HTTP status code
c.status(201)
// Return the response body
return c.body('Thank you for coming')
})
```
You can also write the following.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/welcome', (c) => {
return c.body('Thank you for coming', 201, {
'X-Message': 'Hello!',
'Content-Type': 'text/plain',
})
})
```
The Response is the same as below.
```ts twoslash
new Response('Thank you for coming', {
status: 201,
headers: {
'X-Message': 'Hello!',
'Content-Type': 'text/plain',
},
})
```
## text()
Render text as `Content-Type:text/plain`.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/say', (c) => {
return c.text('Hello!')
})
```
## json()
Render JSON as `Content-Type:application/json`.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/api', (c) => {
return c.json({ message: 'Hello!' })
})
```
## html()
Render HTML as `Content-Type:text/html`.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/', (c) => {
return c.html('
Hello! Hono!
')
})
```
## notFound()
Return the `Not Found` Response.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/notfound', (c) => {
return c.notFound()
})
```
## redirect()
Redirect, default status code is `302`.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/redirect', (c) => {
return c.redirect('/')
})
app.get('/redirect-permanently', (c) => {
return c.redirect('/', 301)
})
```
## res
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
// Response object
app.use('/', async (c, next) => {
await next()
c.res.headers.append('X-Debug', 'Debug message')
})
```
## set() / get()
Get and set arbitrary key-value pairs, with a lifetime of the current request. This allows passing specific values between middleware or from middleware to route handlers.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono<{ Variables: { message: string } }>()
// ---cut---
app.use(async (c, next) => {
c.set('message', 'Hono is cool!!')
await next()
})
app.get('/', (c) => {
const message = c.get('message')
return c.text(`The message is "${message}"`)
})
```
Pass the `Variables` as Generics to the constructor of `Hono` to make it type-safe.
```ts twoslash
import { Hono } from 'hono'
// ---cut---
type Variables = {
message: string
}
const app = new Hono<{ Variables: Variables }>()
```
The value of `c.set` / `c.get` are retained only within the same request. They cannot be shared or persisted across different requests.
## var
You can also access the value of a variable with `c.var`.
```ts twoslash
import type { Context } from 'hono'
declare const c: Context
// ---cut---
const result = c.var.client.oneMethod()
```
If you want to create the middleware which provides a custom method,
write like the following:
```ts twoslash
import { Hono } from 'hono'
import { createMiddleware } from 'hono/factory'
// ---cut---
type Env = {
Variables: {
echo: (str: string) => string
}
}
const app = new Hono()
const echoMiddleware = createMiddleware(async (c, next) => {
c.set('echo', (str) => str)
await next()
})
app.get('/echo', echoMiddleware, (c) => {
return c.text(c.var.echo('Hello!'))
})
```
If you want to use the middleware in multiple handlers, you can use `app.use()`.
Then, you have to pass the `Env` as Generics to the constructor of `Hono` to make it type-safe.
```ts twoslash
import { Hono } from 'hono'
import type { MiddlewareHandler } from 'hono/types'
declare const echoMiddleware: MiddlewareHandler
type Env = {
Variables: {
echo: (str: string) => string
}
}
// ---cut---
const app = new Hono()
app.use(echoMiddleware)
app.get('/echo', (c) => {
return c.text(c.var.echo('Hello!'))
})
```
## render() / setRenderer()
You can set a layout using `c.setRenderer()` within a custom middleware.
```tsx twoslash
/** @jsx jsx */
/** @jsxImportSource hono/jsx */
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.use(async (c, next) => {
c.setRenderer((content) => {
return c.html(
{content}
)
})
await next()
})
```
Then, you can utilize `c.render()` to create responses within this layout.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/', (c) => {
return c.render('Hello!')
})
```
The output of which will be:
```html
Hello!
```
Additionally, this feature offers the flexibility to customize arguments.
To ensure type safety, types can be defined as:
```ts
declare module 'hono' {
interface ContextRenderer {
(
content: string | Promise,
head: { title: string }
): Response | Promise
}
}
```
Here's an example of how you can use this:
```ts
app.use('/pages/*', async (c, next) => {
c.setRenderer((content, head) => {
return c.html(
{head.title}{head.title}
, {
title: 'My hobbies',
})
})
```
## executionCtx
```ts twoslash
import { Hono } from 'hono'
const app = new Hono<{
Bindings: {
KV: any
}
}>()
declare const key: string
declare const data: string
// ---cut---
// ExecutionContext object
app.get('/foo', async (c) => {
c.executionCtx.waitUntil(c.env.KV.put(key, data))
// ...
})
```
## event
```ts twoslash
import { Hono } from 'hono'
declare const key: string
declare const data: string
type KVNamespace = any
// ---cut---
// Type definition to make type inference
type Bindings = {
MY_KV: KVNamespace
}
const app = new Hono<{ Bindings: Bindings }>()
// FetchEvent object (only set when using Service Worker syntax)
app.get('/foo', async (c) => {
c.event.waitUntil(c.env.MY_KV.put(key, data))
// ...
})
```
## env
In Cloudflare Workers Environment variables, secrets, KV namespaces, D1 database, R2 bucket etc. that are bound to a worker are known as bindings.
Regardless of type, bindings are always available as global variables and can be accessed via the context `c.env.BINDING_KEY`.
```ts twoslash
import { Hono } from 'hono'
type KVNamespace = any
// ---cut---
// Type definition to make type inference
type Bindings = {
MY_KV: KVNamespace
}
const app = new Hono<{ Bindings: Bindings }>()
// Environment object for Cloudflare Workers
app.get('/', async (c) => {
c.env.MY_KV.get('my-key')
// ...
})
```
## error
If the Handler throws an error, the error object is placed in `c.error`.
You can access it in your middleware.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.use(async (c, next) => {
await next()
if (c.error) {
// do something...
}
})
```
## ContextVariableMap
For instance, if you wish to add type definitions to variables when a specific middleware is used, you can extend `ContextVariableMap`. For example:
```ts
declare module 'hono' {
interface ContextVariableMap {
result: string
}
}
```
You can then utilize this in your middleware:
```ts twoslash
import { createMiddleware } from 'hono/factory'
// ---cut---
const mw = createMiddleware(async (c, next) => {
c.set('result', 'some values') // result is a string
await next()
})
```
In a handler, the variable is inferred as the proper type:
```ts twoslash
import { Hono } from 'hono'
const app = new Hono<{ Variables: { result: string } }>()
// ---cut---
app.get('/', (c) => {
const val = c.get('result') // val is a string
// ...
return c.json({ result: val })
})
```
# Exception
When a fatal error occurs, such as authentication failure, an HTTPException must be thrown.
## throw HTTPException
This example throws an HTTPException from the middleware.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
declare const authorized: boolean
// ---cut---
import { HTTPException } from 'hono/http-exception'
// ...
app.post('/auth', async (c, next) => {
// authentication
if (authorized === false) {
throw new HTTPException(401, { message: 'Custom error message' })
}
await next()
})
```
You can specify the response to be returned back to the user.
```ts twoslash
import { HTTPException } from 'hono/http-exception'
const errorResponse = new Response('Unauthorized', {
status: 401,
headers: {
Authenticate: 'error="invalid_token"',
},
})
throw new HTTPException(401, { res: errorResponse })
```
## Handling HTTPException
You can handle the thrown HTTPException with `app.onError`.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
import { HTTPException } from 'hono/http-exception'
// ...
app.onError((err, c) => {
if (err instanceof HTTPException) {
// Get the custom response
return err.getResponse()
}
// ...
// ---cut-start---
return c.text('Error')
// ---cut-end---
})
```
## `cause`
The `cause` option is available to add a [`cause`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error/cause) data.
```ts twoslash
import { Hono, Context } from 'hono'
import { HTTPException } from 'hono/http-exception'
const app = new Hono()
declare const message: string
declare const authorize: (c: Context) => void
// ---cut---
app.post('/auth', async (c, next) => {
try {
authorize(c)
} catch (e) {
throw new HTTPException(401, { message, cause: e })
}
await next()
})
```
# App - Hono
`Hono` is the primary object.
It will be imported first and used until the end.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
//...
export default app // for Cloudflare Workers or Bun
```
## Methods
An instance of `Hono` has the following methods.
- app.**HTTP_METHOD**(\[path,\]handler|middleware...)
- app.**all**(\[path,\]handler|middleware...)
- app.**on**(method|method[], path|path[], handler|middleware...)
- app.**use**(\[path,\]middleware)
- app.**route**(path, \[app\])
- app.**basePath**(path)
- app.**notFound**(handler)
- app.**onError**(err, handler)
- app.**mount**(path, anotherApp)
- app.**fire**()
- app.**fetch**(request, env, event)
- app.**request**(path, options)
The first part of them is used for routing, please refer to the [routing section](/docs/api/routing).
## Not Found
`app.notFound` allows you to customize a Not Found Response.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.notFound((c) => {
return c.text('Custom 404 Message', 404)
})
```
## Error Handling
`app.onError` handles an error and returns a customized Response.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.onError((err, c) => {
console.error(`${err}`)
return c.text('Custom Error Message', 500)
})
```
## fire()
`app.fire()` automatically adds a global `fetch` event listener.
This can be useful for environments that adhere to the [Service Worker API](https://developer.mozilla.org/en-US/docs/Web/API/Service_Worker_API), such as [non-ES module Cloudflare Workers](https://developers.cloudflare.com/workers/reference/migrate-to-module-workers/).
`app.fire()` executes the following for you:
```ts
addEventListener('fetch', (event: FetchEventLike): void => {
event.respondWith(this.dispatch(...))
})
```
## fetch()
`app.fetch` will be entry point of your application.
For Cloudflare Workers, you can use the following:
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
type Env = any
type ExecutionContext = any
// ---cut---
export default {
fetch(request: Request, env: Env, ctx: ExecutionContext) {
return app.fetch(request, env, ctx)
},
}
```
or just do:
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
export default app
```
Bun:
```ts
export default app // [!code --]
export default { // [!code ++]
port: 3000, // [!code ++]
fetch: app.fetch, // [!code ++]
} // [!code ++]
```
## request()
`request` is a useful method for testing.
You can pass a URL or pathname to send a GET request.
`app` will return a `Response` object.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
declare const test: (name: string, fn: () => void) => void
declare const expect: (value: any) => any
// ---cut---
test('GET /hello is ok', async () => {
const res = await app.request('/hello')
expect(res.status).toBe(200)
})
```
You can also pass a `Request` object:
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
declare const test: (name: string, fn: () => void) => void
declare const expect: (value: any) => any
// ---cut---
test('POST /message is ok', async () => {
const req = new Request('Hello!', {
method: 'POST',
})
const res = await app.request(req)
expect(res.status).toBe(201)
})
```
## mount()
The `mount()` allows you to mount applications built with other frameworks into your Hono application.
```ts
import { Router as IttyRouter } from 'itty-router'
import { Hono } from 'hono'
// Create itty-router application
const ittyRouter = IttyRouter()
// Handle `GET /itty-router/hello`
ittyRouter.get('/hello', () => new Response('Hello from itty-router'))
// Hono application
const app = new Hono()
// Mount!
app.mount('/itty-router', ittyRouter.handle)
```
## strict mode
Strict mode defaults to `true` and distinguishes the following routes.
- `/hello`
- `/hello/`
`app.get('/hello')` will not match `GET /hello/`.
By setting strict mode to `false`, both paths will be treated equally.
```ts twoslash
import { Hono } from 'hono'
// ---cut---
const app = new Hono({ strict: false })
```
## router option
The `router` option specifices which router to use. The default router is `SmartRouter`. If you want to use `RegExpRouter`, pass it to a new `Hono` instance:
```ts twoslash
import { Hono } from 'hono'
// ---cut---
import { RegExpRouter } from 'hono/router/reg-exp-router'
const app = new Hono({ router: new RegExpRouter() })
```
## Generics
You can pass Generics to specify the types of Cloudflare Workers Bindings and variables used in `c.set`/`c.get`.
```ts twoslash
import { Hono } from 'hono'
type User = any
declare const user: User
// ---cut---
type Bindings = {
TOKEN: string
}
type Variables = {
user: User
}
const app = new Hono<{
Bindings: Bindings
Variables: Variables
}>()
app.use('/auth/*', async (c, next) => {
const token = c.env.TOKEN // token is `string`
// ...
c.set('user', user) // user should be `User`
await next()
})
```
# API
Hono's API is simple.
Just composed by extended objects from Web Standards.
So, you can understand it well quickly.
In this section, we introduce API of Hono like below.
- Hono object
- About routing
- Context object
- About middleware
# Presets
Hono has several routers, each designed for a specific purpose.
You can specify the router you want to use in the constructor of Hono.
**Presets** are provided for common use cases, so you don't have to specify the router each time.
The `Hono` class imported from all presets is the same, the only difference being the router.
Therefore, you can use them interchangeably.
## `hono`
Usage:
```ts twoslash
import { Hono } from 'hono'
```
Routers:
```ts
this.router = new SmartRouter({
routers: [new RegExpRouter(), new TrieRouter()],
})
```
## `hono/quick`
Usage:
```ts twoslash
import { Hono } from 'hono/quick'
```
Router:
```ts
this.router = new SmartRouter({
routers: [new LinearRouter(), new TrieRouter()],
})
```
## `hono/tiny`
Usage:
```ts twoslash
import { Hono } from 'hono/tiny'
```
Router:
```ts
this.router = new PatternRouter()
```
## Which preset should I use?
| Preset | Suitable platforms |
| ------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| `hono` | This is highly recommended for most use cases. Although the registration phase may be slower than `hono/quick`, it exhibits high performance once booted. It's ideal for long-life servers built with **Deno**, **Bun**, or **Node.js**. For environments such as **Cloudflare Workers**, **Deno Deploy**, where v8 isolates are utilized, this preset is suitable as well. Because the isolations persist for a certain amount of time after booting. |
| `hono/quick` | This preset is designed for environments where the application is initialized for every request. **Fastly Compute** operates in this manner, thus this preset is recommended for such use. |
| `hono/tiny` | This is the smallest router package and it's suitable for environments where resources are limited. |
# HonoRequest
The `HonoRequest` is an object that can be taken from `c.req` which wraps a [Request](https://developer.mozilla.org/en-US/docs/Web/API/Request) object.
## param()
Get the values of path parameters.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
// Captured params
app.get('/entry/:id', async (c) => {
const id = c.req.param('id')
// ^?
// ...
})
// Get all params at once
app.get('/entry/:id/comment/:commentId', async (c) => {
const { id, commentId } = c.req.param()
// ^?
})
```
## query()
Get querystring parameters.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
// Query params
app.get('/search', async (c) => {
const query = c.req.query('q')
// ^?
})
// Get all params at once
app.get('/search', async (c) => {
const { q, limit, offset } = c.req.query()
// ^?
})
```
## queries()
Get multiple querystring parameter values, e.g. `/search?tags=A&tags=B`
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/search', async (c) => {
// tags will be string[]
const tags = c.req.queries('tags')
// ^?
// ...
})
```
## header()
Get the request header value.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/', (c) => {
const userAgent = c.req.header('User-Agent')
// ^?
return c.text(`Your user agent is ${userAgent}`)
})
```
::: warning
When `c.req.header()` is called with no arguments, all keys in the returned record are **lowercase**.
If you want to get the value of a header with an uppercase name,
use `c.req.header(“X-Foo”)`.
```ts
// ❌ Will not work
const headerRecord = c.req.header()
const foo = headerRecord['X-Foo']
// ✅ Will work
const foo = c.req.header('X-Foo')
```
:::
## parseBody()
Parse Request body of type `multipart/form-data` or `application/x-www-form-urlencoded`
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.post('/entry', async (c) => {
const body = await c.req.parseBody()
// ...
})
```
`parseBody()` supports the following behaviors.
**Single file**
```ts twoslash
import { Context } from 'hono'
declare const c: Context
// ---cut---
const body = await c.req.parseBody()
const data = body['foo']
// ^?
```
`body['foo']` is `(string | File)`.
If multiple files are uploaded, the last one will be used.
### Multiple files
```ts twoslash
import { Context } from 'hono'
declare const c: Context
// ---cut---
const body = await c.req.parseBody()
body['foo[]']
```
`body['foo[]']` is always `(string | File)[]`.
`[]` postfix is required.
### Multiple files with same name
```ts twoslash
import { Context } from 'hono'
declare const c: Context
// ---cut---
const body = await c.req.parseBody({ all: true })
body['foo']
```
`all` option is disabled by default.
- If `body['foo']` is multiple files, it will be parsed to `(string | File)[]`.
- If `body['foo']` is single file, it will be parsed to `(string | File)`.
### Dot notation
If you set the `dot` option `true`, the return value is structured based on the dot notation.
Imagine receiving the following data:
```ts twoslash
const data = new FormData()
data.append('obj.key1', 'value1')
data.append('obj.key2', 'value2')
```
You can get the structured value by setting the `dot` option `true`:
```ts twoslash
import { Context } from 'hono'
declare const c: Context
// ---cut---
const body = await c.req.parseBody({ dot: true })
// body is `{ obj: { key1: 'value1', key2: 'value2' } }`
```
## json()
Parses the request body of type `application/json`
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.post('/entry', async (c) => {
const body = await c.req.json()
// ...
})
```
## text()
Parses the request body of type `text/plain`
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.post('/entry', async (c) => {
const body = await c.req.text()
// ...
})
```
## arrayBuffer()
Parses the request body as an `ArrayBuffer`
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.post('/entry', async (c) => {
const body = await c.req.arrayBuffer()
// ...
})
```
## blob()
Parses the request body as a `Blob`.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.post('/entry', async (c) => {
const body = await c.req.blob()
// ...
})
```
## formData()
Parses the request body as a `FormData`.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.post('/entry', async (c) => {
const body = await c.req.formData()
// ...
})
```
## valid()
Get the validated data.
```ts
app.post('/posts', async (c) => {
const { title, body } = c.req.valid('form')
// ...
})
```
Available targets are below.
- `form`
- `json`
- `query`
- `header`
- `cookie`
- `param`
See the [Validation section](/docs/guides/validation) for usage examples.
## routePath()
You can retrieve the registered path within the handler like this:
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/posts/:id', (c) => {
return c.json({ path: c.req.routePath })
})
```
If you access `/posts/123`, it will return `/posts/:id`:
```json
{ "path": "/posts/:id" }
```
## matchedRoutes()
It returns matched routes within the handler, which is useful for debugging.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.use(async function logger(c, next) {
await next()
c.req.matchedRoutes.forEach(({ handler, method, path }, i) => {
const name =
handler.name ||
(handler.length < 2 ? '[handler]' : '[middleware]')
console.log(
method,
' ',
path,
' '.repeat(Math.max(10 - path.length, 0)),
name,
i === c.req.routeIndex ? '<- respond from here' : ''
)
})
})
```
## path
The request pathname.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/about/me', async (c) => {
const pathname = c.req.path // `/about/me`
// ...
})
```
## url
The request url strings.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/about/me', async (c) => {
const url = c.req.url // `http://localhost:8787/about/me`
// ...
})
```
## method
The method name of the request.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/about/me', async (c) => {
const method = c.req.method // `GET`
// ...
})
```
## raw
The raw [`Request`](https://developer.mozilla.org/en-US/docs/Web/API/Request) object.
```ts
// For Cloudflare Workers
app.post('/', async (c) => {
const metadata = c.req.raw.cf?.hostMetadata?
// ...
})
```
# Routing
Routing of Hono is flexible and intuitive.
Let's take a look.
## Basic
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
// HTTP Methods
app.get('/', (c) => c.text('GET /'))
app.post('/', (c) => c.text('POST /'))
app.put('/', (c) => c.text('PUT /'))
app.delete('/', (c) => c.text('DELETE /'))
// Wildcard
app.get('/wild/*/card', (c) => {
return c.text('GET /wild/*/card')
})
// Any HTTP methods
app.all('/hello', (c) => c.text('Any Method /hello'))
// Custom HTTP method
app.on('PURGE', '/cache', (c) => c.text('PURGE Method /cache'))
// Multiple Method
app.on(['PUT', 'DELETE'], '/post', (c) =>
c.text('PUT or DELETE /post')
)
// Multiple Paths
app.on('GET', ['/hello', '/ja/hello', '/en/hello'], (c) =>
c.text('Hello')
)
```
## Path Parameter
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/user/:name', async (c) => {
const name = c.req.param('name')
// ^?
// ...
})
```
or all parameters at once:
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/posts/:id/comment/:comment_id', async (c) => {
const { id, comment_id } = c.req.param()
// ^?
// ...
})
```
## Optional Parameter
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
// Will match `/api/animal` and `/api/animal/:type`
app.get('/api/animal/:type?', (c) => c.text('Animal!'))
```
## Regexp
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/post/:date{[0-9]+}/:title{[a-z]+}', async (c) => {
const { date, title } = c.req.param()
// ^?
// ...
})
```
## Including slashes
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/posts/:filename{.+\\.png}', async (c) => {
//...
})
```
## Chained route
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app
.get('/endpoint', (c) => {
return c.text('GET /endpoint')
})
.post((c) => {
return c.text('POST /endpoint')
})
.delete((c) => {
return c.text('DELETE /endpoint')
})
```
## Grouping
You can group the routes with the Hono instance and add them to the main app with the route method.
```ts twoslash
import { Hono } from 'hono'
// ---cut---
const book = new Hono()
book.get('/', (c) => c.text('List Books')) // GET /book
book.get('/:id', (c) => {
// GET /book/:id
const id = c.req.param('id')
return c.text('Get Book: ' + id)
})
book.post('/', (c) => c.text('Create Book')) // POST /book
const app = new Hono()
app.route('/book', book)
```
## Grouping without changing base
You can also group multiple instances while keeping base.
```ts twoslash
import { Hono } from 'hono'
// ---cut---
const book = new Hono()
book.get('/book', (c) => c.text('List Books')) // GET /book
book.post('/book', (c) => c.text('Create Book')) // POST /book
const user = new Hono().basePath('/user')
user.get('/', (c) => c.text('List Users')) // GET /user
user.post('/', (c) => c.text('Create User')) // POST /user
const app = new Hono()
app.route('/', book) // Handle /book
app.route('/', user) // Handle /user
```
## Base path
You can specify the base path.
```ts twoslash
import { Hono } from 'hono'
// ---cut---
const api = new Hono().basePath('/api')
api.get('/book', (c) => c.text('List Books')) // GET /api/book
```
## Routing with hostname
It works fine if it includes a hostname.
```ts twoslash
import { Hono } from 'hono'
// ---cut---
const app = new Hono({
getPath: (req) => req.url.replace(/^https?:\/([^?]+).*$/, '$1'),
})
app.get('/www1.example.com/hello', (c) => c.text('hello www1'))
app.get('/www2.example.com/hello', (c) => c.text('hello www2'))
```
## Routing with `host` Header value
Hono can handle the `host` header value if you set the `getPath()` function in the Hono constructor.
```ts twoslash
import { Hono } from 'hono'
// ---cut---
const app = new Hono({
getPath: (req) =>
'/' +
req.headers.get('host') +
req.url.replace(/^https?:\/\/[^/]+(\/[^?]*)/, '$1'),
})
app.get('/www1.example.com/hello', (c) => c.text('hello www1'))
// A following request will match the route:
// new Request('http://www1.example.com/hello', {
// headers: { host: 'www1.example.com' },
// })
```
By applying this, for example, you can change the routing by `User-Agent` header.
## Routing priority
Handlers or middleware will be executed in registration order.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/book/a', (c) => c.text('a')) // a
app.get('/book/:slug', (c) => c.text('common')) // common
```
```
GET /book/a ---> `a`
GET /book/b ---> `common`
```
When a handler is executed, the process will be stopped.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('*', (c) => c.text('common')) // common
app.get('/foo', (c) => c.text('foo')) // foo
```
```
GET /foo ---> `common` // foo will not be dispatched
```
If you have the middleware that you want to execute, write the code above the handler.
```ts twoslash
import { Hono } from 'hono'
import { logger } from 'hono/logger'
const app = new Hono()
// ---cut---
app.use(logger())
app.get('/foo', (c) => c.text('foo'))
```
If you want to have a "_fallback_" handler, write the code below the other handler.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
// ---cut---
app.get('/bar', (c) => c.text('bar')) // bar
app.get('*', (c) => c.text('fallback')) // fallback
```
```
GET /bar ---> `bar`
GET /foo ---> `fallback`
```
## Grouping ordering
Note that the mistake of grouping routings is hard to notice.
The `route()` function takes the stored routing from the second argument (such as `three` or `two`) and adds it to its own (`two` or `app`) routing.
```ts
three.get('/hi', (c) => c.text('hi'))
two.route('/three', three)
app.route('/two', two)
export default app
```
It will return 200 response.
```
GET /two/three/hi ---> `hi`
```
However, if they are in the wrong order, it will return a 404.
```ts twoslash
import { Hono } from 'hono'
const app = new Hono()
const two = new Hono()
const three = new Hono()
// ---cut---
three.get('/hi', (c) => c.text('hi'))
app.route('/two', two) // `two` does not have routes
two.route('/three', three)
export default app
```
```
GET /two/three/hi ---> 404 Not Found
```
) : (
)}