Cloudflare Workers Documentation

Cloudflare Workers provides a serverless execution environment that allows you to create entirely new applications or augment existing ones without configuring or maintaining infrastructure.

Quick Start

Get Started Begin building and publishing your code from the CLI.

Tutorials

Discover what you can build with these step-by-step tutorials.

Build an Application Create a Slack Bot for GitHub
Build a Serverless Function Deploy a QR code generator
Configure Your CDN Serve and cache files from cloud storage

Templates

Ready-to-use code to get you started.

Hello World

Simple Hello World in JS

Paste this into your terminal:


        wrangler generate my-app
        https://github.com/cloudflare/worker-template

Demo

Hello World Rust

Simple Hello World in Rust

Paste this into your terminal:


        wrangler generate my-app
        https://github.com/cloudflare/rustwasm-worker-template

Demo

Bulk Redirects

Redirects requests to certain URLs based a mapped object to the request’s URL.

Copy into a Worker script:

async function handleRequest(request) {
  let requestURL = new URL(request.url)
  let path = requestURL.pathname.split('/redirect')[1]
  let location = redirectMap.get(path)
  if (location) {
    return Response.redirect(location, 301)
  }
  // If in map, return the original request
  return fetch(request)
}
addEventListener('fetch', async event => {
  event.respondWith(handleRequest(event.request))
})
const externalHostname = 'workers-tooling.cf'
const redirectMap = new Map([
  ['/bulk1', 'https://' + externalHostname + '/redirect2'],
  ['/bulk2', 'https://' + externalHostname + '/redirect3'],
  ['/bulk3', 'https://' + externalHostname + '/redirect4'],
  ['/bulk4', 'https://google.com'],
])

Demo

Send Raw HTML

Delivers an HTML page from HTML directly in the Worker script.

Copy into a Worker script:

async function handleRequest(request) {
  const init = {
    headers: {
      'content-type': 'text/html;charset=UTF-8',
    },
  }
  return new Response(someHTML, init)
}
addEventListener('fetch', event => {
  return event.respondWith(handleRequest(event.request))
})
const someHTML =  `<!DOCTYPE html>
<html>
  <body>
  <h1>Hello World</h1>
  <p>This is all generated using a Worker</p>
  <iframe
      width="560"
      height="315"
      src="https://www.youtube.com/embed/dQw4w9WgXcQ"
      frameborder="0"
      allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture"
      allowfullscreen
  ></iframe>
  </body>
</html>
`

Demo

View all templates

Reference

Runtime APIs

Global variables immediately available in your code

Concepts

The need to know while writing Workers scripts.

Tooling

Build and deploy with integrated tools