Cloudflare Worker Reverse Proxy Tutorial

What is a reverse proxy?#

A reverse proxy accesses the target site on your behalf and then returns the result. For example, instead of directly visiting example.com, you let Cloudflare Worker request it and return the response.

Typical use cases:

Bypass geo restrictions
Hide your real server address
Access blocked websites
Use your own domain to access target websites

Prerequisites#

Cloudflare account - sign up for free at https://cloudflare.com
Wrangler CLI - npm install -g wrangler
Wrangler login - wrangler login

Demo project (proxying an AI public relay site)#

Repository: https://github.com/evepupil/any-proxy

Live demo: any.chaosyn.com

Note: direct access only works after binding a custom domain.

Full code example#

Create worker.js:

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/**
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 * Cloudflare Worker reverse proxy
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 * Purpose: proxy anyrouter.top
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 */
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// Target website
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const TARGET_HOST = 'anyrouter.top';
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const TARGET_URL = `https://${TARGET_HOST}`;
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addEventListener('fetch', event => {
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  event.respondWith(handleRequest(event.request));
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});
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/**
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 * Core request handler
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 */
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async function handleRequest(request) {
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  try {
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    // 1. Parse incoming URL
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    const url = new URL(request.url);
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    // 2. Build target URL (keep original path and query)
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    const targetUrl = `${TARGET_URL}${url.pathname}${url.search}`;
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    // 3. Copy and adjust headers
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    const headers = new Headers(request.headers);
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    headers.set('Host', TARGET_HOST);
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    // 4. Build request options
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    const requestOptions = {
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      method: request.method,
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      headers: headers,
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      // Important: do not follow redirects automatically
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      redirect: 'manual',
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    };
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    // 5. Forward request
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    const response = await fetch(targetUrl, requestOptions);
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    // 6. Handle redirect responses
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    if ([301, 302, 303, 307, 308].includes(response.status)) {
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      const location = response.headers.get('Location');
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      if (location && !location.startsWith(TARGET_HOST)) {
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        // Forward external redirect
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        const responseHeaders = new Headers(response.headers);
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        responseHeaders.set('Access-Control-Allow-Origin', '*');
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        return new Response(response.body, {
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          status: response.status,
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          statusText: response.statusText,
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          headers: responseHeaders
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        });
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      } else {
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        // Block self-redirect loops
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        return new Response('This site does not allow proxy access', {
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          status: 200,
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          headers: { 'Content-Type': 'text/plain; charset=utf-8' }
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        });
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      }
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    }
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    // 7. Handle normal response
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    const responseHeaders = new Headers(response.headers);
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    responseHeaders.set('Access-Control-Allow-Origin', '*');
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    responseHeaders.set('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS');
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    // 8. Remove conflicting security headers
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    responseHeaders.delete('Content-Security-Policy');
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    responseHeaders.delete('X-Frame-Options');
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    // 9. Return response
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    return new Response(response.body, {
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      status: response.status,
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      statusText: response.statusText,
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      headers: responseHeaders
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    });
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  } catch (error) {
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    return new Response(`Proxy failed: ${error.message}`, {
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      status: 500,
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      headers: { 'Content-Type': 'text/plain; charset=utf-8' }
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    });
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  }
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}

Deployment steps#

Method 1: CLI (recommended)#

1. Initialize project

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wrangler init any-proxy
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cd any-proxy

2. Create config file wrangler.toml

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name = "any-proxy"
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main = "worker.js"
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compatibility_date = "2024-01-01"
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workers_dev = true

3. Deploy

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wrangler deploy

4. Get URL
After deployment, you will see output like:

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Deployed any-proxy triggers (0.66 sec)
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  https://any-proxy.your-subdomain.workers.dev

That URL is your proxy endpoint.

Method 2: Dashboard#

Log in to Cloudflare Dashboard
Go to “Workers & Pages”
Click “Create application” → “Create Worker”
Paste your code
Click “Save and Deploy”

Bind a custom domain#

1. Add domain in Cloudflare

If your-domain.com is managed by Cloudflare:

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# Add route to wrangler.toml
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routes = [
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  { pattern = "your-domain.com/*", zone_name = "your-domain.com" }
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]

2. Redeploy

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wrangler deploy

3. DNS settings

Cloudflare handles DNS records automatically, so manual DNS setup is usually unnecessary.

Common issues#

❌ 500 error - “Too many redirects”#

Cause: target site detects proxy access and keeps redirecting.

Fix: set redirect: 'manual' and handle redirects yourself (see code above).

❌ Static assets return 404#

Cause: internal links are absolute URLs pointing to the origin domain.

Fix: add URL rewriting to replace origin-domain links with your proxy domain.

❌ CORS errors#

Fix: include these response headers:

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Access-Control-Allow-Origin: *
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Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS

Advanced features#

1. URL rewrite (force all resources through proxy)#

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// Add this in response handling
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const contentType = response.headers.get('content-type') || '';
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if (contentType.includes('text/html') ||
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    contentType.includes('text/javascript') ||
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    contentType.includes('text/css')) {
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  const text = await response.text();
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  // Replace anyrouter.top with current proxy domain
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  const rewrittenText = text.replace(/https:\/\/anyrouter\.top/g, proxyUrl);
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  return new Response(rewrittenText, {
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    status: response.status,
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    headers: responseHeaders
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  });
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}

2. Add caching#

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// Cache static assets for 1 hour
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const cacheKey = new Request(url, request);
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const cache = caches.default;
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let response = await cache.match(cacheKey);
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if (!response) {
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  response = await fetch(targetUrl);
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  // Store response in cache
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  await cache.put(cacheKey, response.clone());
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}

Example project structure#

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my-proxy/
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├── worker.js          # Main program
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├── wrangler.toml      # Configuration
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└── package.json       # Dependencies (optional)

Summary#

Core flow: intercept request → forward to target → adjust response → return to client
Key points:
- Adjust request headers (Host, Origin)
- Disable auto-redirects
- Add CORS support
- Handle URL rewriting
Deployment options: Wrangler CLI or Dashboard UI

That’s it. You can now access target websites anywhere through your Cloudflare Worker.

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