Server#

Rsbuild comes with a built-in dev server designed to improve the development experience. When you run the rsbuild dev or rsbuild preview commands, the server will start, providing features such as page preview, routing, and hot module reloading.

Page Routing#

Rsbuild Server offers a set of default routing convention, and allows users to customize it through configurations.

Default Behavior#

Rsbuild Server will generate the corresponding page route based on the source.entry configuration.

When entry is index, the page can be accessed through /; when entry is foo, the page can be accessed through /foo.

export default {
  source: {
    entry: {
      index: './src/index.ts',
      foo: './src/pages/foo/index.ts',
    },
  },
};

Fallback Behavior#

By default, when the request meets the following conditions and the corresponding resource is not found, it will fallback to index.html:

• The request is a GET or HEAD request
• Which accepts text/html (the request header accept type is text/html or */*)

export default {
  server: {
    htmlFallback: 'index',
  },
};

Custom Fallback Behavior#

When Rsbuild's default server.htmlFallback configuration cannot meet your needs, for example, if you want to be able to access main.html when accessing /, you can set it up using server.historyApiFallback.

export default {
  source: {
    entry: {
      main: './src/index.ts',
    },
  },
  server: {
    htmlFallback: false,
    historyApiFallback: {
      index: '/main.html',
    },
  },
};

HTML Output Path#

Normally, / points to the dist root directory, and the HTML file is output to the dist root directory. At this time, the corresponding HTML page can be accessed through /some-path.

If you output HTML files to other subdirectories by modifying output.distPath.html, you need to access the corresponding HTML page through /[htmlPath]/some-path.

For example, if you set the HTML file to be output to the HTML directory, index.html will be accessed through /html/, and foo.html will be accessed through /html/foo.

export default {
  source: {
    entry: {
      index: './src/index.ts',
      foo: './src/pages/foo/index.ts',
    },
  },
  output: {
    distPath: {
      html: 'html',
    },
  },
};

Rspack Dev Server#

The built-in dev server of Rspack CLI is @rspack/dev-server. Rsbuild does not use @rspack/dev-server, but implements a lighter version based on webpack-dev-middleware.

Comparison#

The dev server of Rsbuild and @rspack/dev-server have the following differences:

• Configuration: Rsbuild provides richer server configuration options.
• Log Format: The log format of Rspack CLI is basically consistent with Webpack CLI, while Rsbuild's logs are clearer and more readable.
• Dependencies: @rspack/dev-server is based on express with many third-party dependencies. Rsbuild, on the other hand, uses lighter libraries such as connect.

Configuration#

Rsbuild does not support using Rspack's devServer config. Instead, you can use Rsbuild's dev and server configs.

In Rsbuild, dev contains some configs that are only work during development, while the server config works for both dev and preview servers.

Below are the Rsbuild configs that correspond to the Rspack CLI's devServer config:

For more configurations, please refer to Config Overview.

Extend middleware#

Rsbuild server does not use any Node.js frameworks, and the req and res provided by Rsbuild middleware are both native Node.js objects.

This means that when you migrate from other server-side frameworks (such as Express), the original middleware may not necessarily be used directly in Rsbuild. For example, the req.params,req.path, req.search, req.query and other properties provided by Express cannot be accessed in the Rsbuild middleware.

If you need to use existing middleware in Rsbuild, this can be done by passing the server application as middleware as follows:

import expressMiddleware from 'my-express-middleware';
import express from 'express';

// Initialize Express app
const app = express();

app.use(expressMiddleware);

export default {
  dev: {
    setupMiddlewares: [
      (middleware) => {
        middleware.unshift(app);
      },
    ],
  },
};

Custom Server#

If you want to integrate Rsbuild dev server into a custom server, you can get the instance methods of Rsbuild dev server through the createDevServer method of Rsbuild and call them on demand.

For details, please refer to Rsbuild - createDevServer.