---
title: Fetch Handler
description: Handle incoming HTTP requests in Cloudflare Workers using the fetch() handler and return responses.
image: https://developers.cloudflare.com/dev-products-preview.png
---

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# Fetch Handler

## Background

Incoming HTTP requests to a Worker are passed to the `fetch()` handler as a [Request](https://developers.cloudflare.com/workers/runtime-apis/request/) object. To respond to the request with a response, return a [Response](https://developers.cloudflare.com/workers/runtime-apis/response/) object:

JavaScript

```
export default {  async fetch(request, env, ctx) {    return new Response('Hello World!');  },};
```

Note

The Workers runtime does not support `XMLHttpRequest` (XHR). Learn the difference between `XMLHttpRequest` and `fetch()` in the [MDN ↗](https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest) documentation.

### Parameters

* `request` Request

  * The incoming HTTP request.
* `env` object

  * The [bindings](https://developers.cloudflare.com/workers/runtime-apis/bindings/) available to the Worker. As long as the [environment](https://developers.cloudflare.com/workers/wrangler/environments/) has not changed, the same object (equal by identity) may be passed to multiple requests. You can also [import env from cloudflare:workers](https://developers.cloudflare.com/workers/runtime-apis/bindings/#importing-env-as-a-global) to access bindings from anywhere in your code.
* `ctx.waitUntil(promisePromise)` : void

  * Refer to [waitUntil](https://developers.cloudflare.com/workers/runtime-apis/context/#waituntil).
* `ctx.passThroughOnException()` : void

  * Refer to [passThroughOnException](https://developers.cloudflare.com/workers/runtime-apis/context/#passthroughonexception).

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