---
title: Multiple Workers
description: Miniflare allows you to run multiple workers in the same instance. All Workers can be defined at the same level, using the workers option.
image: https://developers.cloudflare.com/dev-products-preview.png
---

> Documentation Index  
> Fetch the complete documentation index at: https://developers.cloudflare.com/workers/llms.txt  
> Use this file to discover all available pages before exploring further.

[Skip to content](#%5Ftop) 

# Multiple Workers

Miniflare allows you to run multiple workers in the same instance. All Workers can be defined at the same level, using the `workers` option.

Here's an example that uses a service binding to increment a value in a shared KV namespace:

JavaScript

```

import { Miniflare, Response } from "miniflare";


const message = "The count is ";

const mf = new Miniflare({

  // Options shared between workers such as HTTP and persistence configuration

  // should always be defined at the top level.

  host: "0.0.0.0",

  port: 8787,

  kvPersist: true,


  workers: [

    {

      name: "worker",

      kvNamespaces: { COUNTS: "counts" },

      serviceBindings: {

        INCREMENTER: "incrementer",

        // Service bindings can also be defined as custom functions, with access

        // to anything defined outside Miniflare.

        async CUSTOM(request) {

          // `request` is the incoming `Request` object.

          return new Response(message);

        },

      },

      modules: true,

      script: `export default {

        async fetch(request, env, ctx) {

          // Get the message defined outside

          const response = await env.CUSTOM.fetch("http://host/");

          const message = await response.text();


          // Increment the count 3 times

          await env.INCREMENTER.fetch("http://host/");

          await env.INCREMENTER.fetch("http://host/");

          await env.INCREMENTER.fetch("http://host/");

          const count = await env.COUNTS.get("count");


          return new Response(message + count);

        }

      }`,

    },

    {

      name: "incrementer",

      // Note we're using the same `COUNTS` namespace as before, but binding it

      // to `NUMBERS` instead.

      kvNamespaces: { NUMBERS: "counts" },

      // Worker formats can be mixed-and-matched

      script: `addEventListener("fetch", (event) => {

        event.respondWith(handleRequest());

      })

      async function handleRequest() {

        const count = parseInt((await NUMBERS.get("count")) ?? "0") + 1;

        await NUMBERS.put("count", count.toString());

        return new Response(count.toString());

      }`,

    },

  ],

});

const res = await mf.dispatchFetch("http://localhost");

console.log(await res.text()); // "The count is 3"

await mf.dispose();


```

## Routing

You can enable routing by specifying `routes` via the API, using the[standard route syntax](https://developers.cloudflare.com/workers/configuration/routing/routes/#matching-behavior). Note port numbers are ignored:

JavaScript

```

const mf = new Miniflare({

  workers: [

    {

      scriptPath: "./api/worker.js",

      routes: ["http://127.0.0.1/api*", "api.mf/*"],

    },

  ],

});


```

When using hostnames that aren't `localhost` or `127.0.0.1`, you may need to edit your computer's `hosts` file, so those hostnames resolve to`localhost`. On Linux and macOS, this is usually at `/etc/hosts`. On Windows, it's at `C:\Windows\System32\drivers\etc\hosts`. For the routes above, we would need to append the following entries to the file:

```

127.0.0.1 miniflare.test

127.0.0.1 api.mf


```

Alternatively, you can customise the `Host` header when sending the request:

Terminal window

```

# Dispatches to the "api" worker

$ curl "http://localhost:8787/todos/update/1" -H "Host: api.mf"


```

When using the API, Miniflare will use the request's URL to determine which Worker to dispatch to.

JavaScript

```

// Dispatches to the "api" worker

const res = await mf.dispatchFetch("http://api.mf/todos/update/1", { ... });


```

## Durable Objects

Miniflare supports the `script_name` option for accessing Durable Objects exported by other scripts. See[📌 Durable Objects](https://developers.cloudflare.com/workers/testing/miniflare/storage/durable-objects#using-a-class-exported-by-another-script)for more details.

```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/testing/","name":"Testing"}},{"@type":"ListItem","position":4,"item":{"@id":"/workers/testing/miniflare/","name":"Miniflare"}},{"@type":"ListItem","position":5,"item":{"@id":"/workers/testing/miniflare/core/","name":"Core"}},{"@type":"ListItem","position":6,"item":{"@id":"/workers/testing/miniflare/core/multiple-workers/","name":"Multiple Workers"}}]}
```