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 ApplicationCreate a Slack Bot for GitHub
Build a Serverless FunctionDeploy a QR code generator
Deploy a Static SiteGet Started with create-react-app

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

Hello World Rust

Simple Hello World in Rust

Paste this into your terminal:

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

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'],
])

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>
`

View all templates

Reference

Runtime APIs

Global variables immediately available in your code

About

Learn about the Workers platform.

Tooling

Build and deploy with integrated tools

Licenses