---
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://edgetunnel-b2h.pages.dev/dev-products-preview.png
---

> Documentation Index  
> Fetch the complete documentation index at: https://edgetunnel-b2h.pages.dev/workers/llms.txt  
> Use this file to discover all available pages before exploring further. 

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# 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**

```js
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://edgetunnel-b2h.pages.dev/workers/configuration/routing/routes/#matching-behavior). Note port numbers are ignored:

**JavaScript**

```js
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:

```plaintext
127.0.0.1 miniflare.test
127.0.0.1 api.mf
```

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

```sh
# 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**

```js
// 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://edgetunnel-b2h.pages.dev/workers/testing/miniflare/storage/durable-objects#using-a-class-exported-by-another-script)for more details.

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