> For AI agents: the complete documentation index is available at /llms.txt, the full documentation bundle is available at /llms-full.txt.

# Dev server

The `rspack dev` and `rspack serve` commands run a local development server through [@rspack/dev-server](https://npmjs.com/package/@rspack/dev-server). It provides hot module replacement (HMR), static file serving, proxying, and related development features.

## Install dev server

`@rspack/dev-server` is an optional peer dependency of `@rspack/cli`.

Install it before using `rspack dev`, `rspack serve`, or `rspack preview`:


```sh [npm]
npm add @rspack/dev-server -D
```

```sh [yarn]
yarn add @rspack/dev-server -D
```

```sh [pnpm]
pnpm add @rspack/dev-server -D
```

```sh [bun]
bun add @rspack/dev-server -D
```

```sh [deno]
deno add npm:@rspack/dev-server -D
```

## HMR

By default, Rspack enables HMR in dev mode. You can disable HMR by configuring the `devServer.hot` option in Rspack configuration.

```js title="rspack.config.mjs"
export default {
  devServer: {
    hot: false,
  },
};
```

:::warning
Do not include `[hash]` or `[contenthash]` in [output.cssFilename](/config/output.md#outputcssfilename), otherwise CSS HMR may not work.
:::

## Proxy

The dev server includes proxy support. Configure the `devServer.proxy` option to proxy matching requests. This feature is powered by [http-proxy-middleware](https://github.com/chimurai/http-proxy-middleware). For example, you can proxy `/api` to `http://localhost:3000` as follows:

```js title="rspack.config.mjs"
export default {
  devServer: {
    proxy: [
      {
        context: ['/api'],
        target: 'http://localhost:3000',
        changeOrigin: true,
      },
    ],
  },
};
```

For more devServer configuration options, please refer to [devServer](/config/dev-server.md).