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Adapter Helper

The Adapter Helper provides a seamless way to interact with various platforms through a unified interface.


import { Hono } from 'hono'
import { env, getRuntimeKey } from 'hono/adapter'


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.

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:

Specify the runtime

You can specify the runtime to get environment variables by passing the runtime key as the second argument.

app.get('/env', (c) => {
  const { NAME } = env<{ NAME: string }>(c, 'workerd')
  return c.text(NAME)


The getRuntimeKey() function returns the identifier of the current runtime.

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:

  • workerd - Cloudflare Workers
  • deno
  • bun
  • node
  • edge-light - Vercel Edge Functions
  • fastly - Fastly Compute
  • other - Other unknown runtimes keys

Released under the MIT License.