Alter headers
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Alter headers

Example of how to add, change, or delete headers sent in a request or returned in a response.

Last updated Apr 23, 2026 If you want to get started quickly, click on the button below.

This creates a repository in your GitHub account and deploys the application to Cloudflare Workers.

export default {
    async fetch(request) {
        const response = await fetch("https://example.com");

        // Clone the response so that it's no longer immutable
        const newResponse = new Response(response.body, response);

        // Add a custom header with a value
        newResponse.headers.append(
            "x-workers-hello",
            "Hello from Cloudflare Workers",
        );

        // Delete headers
        newResponse.headers.delete("x-header-to-delete");
        newResponse.headers.delete("x-header2-to-delete");

        // Adjust the value for an existing header
        newResponse.headers.set("x-header-to-change", "NewValue");

        return newResponse;
    },
};

export default {
    async fetch(request): Promise<Response> {
        const response = await fetch(request);

        // Clone the response so that it's no longer immutable
        const newResponse = new Response(response.body, response);

        // Add a custom header with a value
        newResponse.headers.append(
            "x-workers-hello",
            "Hello from Cloudflare Workers",
        );

        // Delete headers
        newResponse.headers.delete("x-header-to-delete");
        newResponse.headers.delete("x-header2-to-delete");

        // Adjust the value for an existing header
        newResponse.headers.set("x-header-to-change", "NewValue");

        return newResponse;
    },
} satisfies ExportedHandler;

from workers import Response, fetch, WorkerEntrypoint

class Default(WorkerEntrypoint):
  async def fetch(self, request):
      response = await fetch("https://example.com")

      # Grab the response headers so they can be modified
      new_headers = response.headers

      # Add a custom header with a value
      new_headers["x-workers-hello"] = "Hello from Cloudflare Workers"

      # Delete headers
      if "x-header-to-delete" in new_headers:
          del new_headers["x-header-to-delete"]
      if "x-header2-to-delete" in new_headers:
          del new_headers["x-header2-to-delete"]

      # Adjust the value for an existing header
      new_headers["x-header-to-change"] = "NewValue"

      return Response(response.body, headers=new_headers)

import { Hono } from 'hono';

const app = new Hono();

app.use('*', async (c, next) => {
  // Process the request with the next middleware/handler
  await next();

  // After the response is generated, we can modify its headers

  // Add a custom header with a value
  c.res.headers.append(
    "x-workers-hello",
    "Hello from Cloudflare Workers with Hono"
  );

  // Delete headers
  c.res.headers.delete("x-header-to-delete");
  c.res.headers.delete("x-header2-to-delete");

  // Adjust the value for an existing header
  c.res.headers.set("x-header-to-change", "NewValue");
});

app.get('*', async (c) => {
  // Fetch content from example.com
  const response = await fetch("https://example.com");

  // Return the response body with original headers
  // (our middleware will modify the headers before sending)
  return new Response(response.body, {
    headers: response.headers
  });
});

export default app;

You can also use the custom-headers-example template ↗︎ to deploy this code to your custom domain.

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Alter headers

Alter headers

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