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      • Dev server

      The rspack dev and rspack serve commands run a local development server through @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:

      npm
      yarn
      pnpm
      bun
      deno
      npm add @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.

      rspack.config.mjs
      export default {
  devServer: {
    hot: false,
  },
};
      Warning

      Do not include [hash] or [contenthash] in output.cssFilename, 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. For example, you can proxy /api to http://localhost:3000 as follows:

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

      For more devServer configuration options, please refer to devServer.