---
title: Handlers
description: Methods, such as `fetch()`, on Workers that can receive and process external inputs.
image: https://developers.cloudflare.com/dev-products-preview.png
---

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# Handlers

Handlers are methods on Workers that can receive and process external inputs, and can be invoked from outside your Worker. For example, the `fetch()` handler receives an HTTP request, and can return a response:

JavaScript

```

export default {

  async fetch(request, env, ctx) {

    return new Response('Hello World!');

  },

};


```

The following handlers are available within Workers:

* [ Alarm Handler ](https://developers.cloudflare.com/durable-objects/api/alarms/)
* [ Email Handler ](https://developers.cloudflare.com/email-routing/email-workers/runtime-api/)
* [ Fetch Handler ](https://developers.cloudflare.com/workers/runtime-apis/handlers/fetch/)
* [ Queue Handler ](https://developers.cloudflare.com/queues/configuration/javascript-apis/#consumer)
* [ Scheduled Handler ](https://developers.cloudflare.com/workers/runtime-apis/handlers/scheduled/)
* [ Tail Handler ](https://developers.cloudflare.com/workers/runtime-apis/handlers/tail/)

## Handlers in Python Workers

When you [write Workers in Python](https://developers.cloudflare.com/workers/languages/python/), handlers are placed in a class named `Default` that extends the [WorkerEntrypoint class](https://developers.cloudflare.com/workers/runtime-apis/bindings/service-bindings/rpc/) (which you can import from the `workers` SDK module).

```json
{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/directory/","name":"Directory"}},{"@type":"ListItem","position":2,"item":{"@id":"/workers/","name":"Workers"}},{"@type":"ListItem","position":3,"item":{"@id":"/workers/runtime-apis/","name":"Runtime APIs"}},{"@type":"ListItem","position":4,"item":{"@id":"/workers/runtime-apis/handlers/","name":"Handlers"}}]}
```