Examples

• Return small HTML page

  Deliver an HTML page from an HTML string directly inside the Worker script.

• Return JSON

  Return JSON directly from a Worker script, useful for building APIs and middleware.

• Fetch HTML

  Send a request to a remote server, read HTML from the response, and serve that HTML.

• Fetch JSON

  Send a GET request and read in JSON from the response. Use to fetch external data.

• Redirect

  Redirect requests from one URL to another or from one set of URLs to another set.

• Accessing the object

  Access custom Cloudflare properties and control how Cloudflare features are applied to every request.

• Respond with another site

  Respond to the Worker request with the response from another website (example.com in this example).

• A/B testing with same-URL direct access

  Set up an A/B test by controlling what response is served based on cookies. This version supports passing the request through to test and control on the origin, bypassing random assignment.

• Aggregate requests

  Send two GET request to two urls and aggregates the responses into one response.

• Alter headers

  Change the headers sent in a request or returned in a response.

• Auth with headers

  Allow or deny a request based on a known pre-shared key in a header. This is not meant to replace the WebCrypto API.

• Block on TLS

  Inspects the incoming request's TLS version and blocks if under TLSv1.2.

• Bulk origin override

  Resolve requests to your domain to a set of proxy third-party origin URLs.

• Bulk redirects

  Redirect requests to certain URLs based on a mapped object to the request's URL.

• Cache POST requests

  Cache POST requests using the Cache API.

• Cache using fetch

  Determine how to cache a resource by setting TTLs, custom cache keys, and cache headers in a fetch request.

• Conditional response

  Return a response based on the incoming request's URL, HTTP method, User Agent, IP address, ASN or device type.

• Cookie parsing

  Given the cookie name, get the value of a cookie. You can also use cookies for A/B testing.

• CORS header proxy

  Add the necessary CORS headers to a third party API response.

• Country code redirect

  Redirect a response based on the country code in the header of a visitor.

• Data loss prevention

  Protect sensitive data to prevent data loss, and send alerts to a webhooks server in the event of a data breach.

• Debugging logs

  Send debugging information in an errored response to a logging service.

• Geolocation: Custom Styling

  Personalize website styling based on localized user time.

• Geolocation: Hello World

  Get all geolocation data fields and display them in HTML.

• Geolocation: Weather application

  Fetch weather data from an API using the user's geolocation data.

• Hot-link protection

  Block other websites from linking to your content. This is useful for protecting images.

• HTTP Basic Authentication

  Shows how to restrict access using the HTTP Basic schema.

• HTTP2 server push

  Push static assets to a client's browser without waiting for HTML to render.

• Logging headers to console

  Examine the contents of a Headers object by logging to console with a Map.

• Modify request property

  Create a modified request with edited properties based off of an incoming request.

• Modify response

  Fetch and modify response properties which are immutable by creating a copy first.

• Multiple Cron Triggers

  Set multiple Cron Triggers on three different schedules.

• Post JSON

  Send a POST request with JSON data. Use to share data with external servers.

• Read POST

  Serve an HTML form, then read POST requests. Use also to read JSON or POST data from an incoming request.

• Rewrite links

  Rewrite URL links in HTML using the HTMLRewriter. This is useful for JAMstack websites.

• Set security headers

  Set common security headers (X-XSS-Protection, X-Frame-Options, X-Content-Type-Options, Permissions-Policy, Referrer-Policy, Strict-Transport-Security, Content-Security-Policy).

• Setting Cron Triggers

  Set a Cron Trigger for your Worker.

• Sign requests

  Sign and verify a request using the HMAC and SHA-256 algorithms or return a 403.

• Using the Cache API

  Use the Cache API to store responses in Cloudflare's cache.