Examples

Explore the following examples for Workers.

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103 Early Hints

Allow a client to request static assets while waiting for the HTML response.

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.

Accessing the Cloudflare Object

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

Aggregate requests

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

Alter headers

Example of how to add, change, or delete 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.

HTTP Basic Authentication

Shows how to restrict access using the HTTP Basic schema.

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.

Using the Cache API

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

Cache POST requests

Cache POST requests using the Cache API.

Cache Tags using Workers

Send Additional Cache Tags using Workers

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.

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.

Setting Cron Triggers

Set a Cron Trigger for your Worker.

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.

Cookie parsing

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

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.

Geolocation: Weather application

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

Geolocation: Custom Styling

Personalize website styling based on localized user time.

Geolocation: Hello World

Get all geolocation data fields and display them in HTML.

Hot-link protection

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

Custom Domain with Images

Set up custom domain for Images using a Worker or serve images using a prefix path and Cloudflare registered domain.

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.

Stream OpenAI API Responses

Use the OpenAI v4 SDK to stream responses from OpenAI.

Post JSON

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

Using timingSafeEqual

Protect against timing attacks by safely comparing values using `timingSafeEqual`.

Redirect

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

Read POST

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

Return small HTML page

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

Respond with another site

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

Return JSON

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

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).

Sign requests

Verify a signed request using the HMAC and SHA-256 algorithms or return a 403.

Turnstile with Workers

Inject [Turnstile](/turnstile/) implicitly into HTML elements using the HTMLRewriter runtime API.

Using the WebSockets API

Use the WebSockets API to communicate in real time with your Cloudflare Workers.