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      • Plugin hooks

      This page outlines the plugin hooks available for Rsbuild plugins.

      Overview

      Common hooks

      Dev hooks

      Called when running the rsbuild dev command or the rsbuild.startDevServer() method:

      Build hooks

      Called when running the rsbuild build command or the rsbuild.build() method:

      • onBeforeBuild: Called before running the production build.
      • onAfterBuild: Called after running the production build. You can get the build result information.
      • onCloseBuild: Called when the build is closed.

      Preview hooks

      Called when running the rsbuild preview command or the rsbuild.preview() method:

      Hooks order

      Dev hooks

      When the rsbuild dev command or rsbuild.startDevServer() method is executed, Rsbuild will execute the following hooks in order:

      When rebuilding, the following hooks will be triggered again:

      Build hooks

      When the rsbuild build command or rsbuild.build() method is executed, Rsbuild will execute the following hooks in order:

      When rebuilding, the following hooks will be triggered again:

      Preview hooks

      When executing the rsbuild preview command or rsbuild.preview() method, Rsbuild will execute the following hooks in order:

      Global hooks vs environment hooks

      In Rsbuild, some plugin hooks are global. These hooks relate to Rsbuild's startup process or other shared logic and run across all environments. For example:

      • modifyRsbuildConfig is used to modify the basic configuration of Rsbuild. The basic configuration will eventually be merged with the environment configuration;
      • onBeforeStartDevServer and onAfterStartDevServer are related to the Rsbuild dev server startup process, all environments share Rsbuild's dev server, middleware, and WebSocket.

      Correspondingly, there are some plugin hooks that are related to the current environment. These hooks are executed with a specific environment context and are triggered multiple times depending on the environment.

      Global hooks

      Environment hooks

      Callback order

      Default behavior

      If multiple plugins register the same hook, the callback functions of the hook will execute in the order in which they were registered.

      In the following example, the console will output '1' and '2' in sequence:

      const plugin1 = () => ({
  setup(api) {
    api.modifyRsbuildConfig(() => console.log('1'));
  },
});

const plugin2 = () => ({
  setup(api) {
    api.modifyRsbuildConfig(() => console.log('2'));
  },
});

rsbuild.addPlugins([plugin1, plugin2]);

      order Field

      When registering a hook, you can declare the order of hook through the order field.

      type HookDescriptor<T extends (...args: any[]) => any> = {
  handler: T;
  order: 'pre' | 'post' | 'default';
};

      In the following example, the console will sequentially output '2' and '1', because order was set to pre when plugin2 called modifyRsbuildConfig.

      const plugin1 = () => ({
  setup(api) {
    api.modifyRsbuildConfig(() => console.log('1'));
  },
});

const plugin2 = () => ({
  setup(api) {
    api.modifyRsbuildConfig({
      handler: () => console.log('2'),
      order: 'pre',
    });
  },
});

rsbuild.addPlugins([plugin1, plugin2]);

      Common hooks

      modifyRsbuildConfig

      Modify the config passed to the Rsbuild, you can directly modify the config object, or return a new object to replace the previous object.

      Warning

      modifyRsbuildConfig is a global hook. To add support for your plugin as an environment-specific plugin, you should use modifyEnvironmentConfig instead of modifyRsbuildConfig.

      • Type:
      type ModifyRsbuildConfigUtils = {
  mergeRsbuildConfig: typeof mergeRsbuildConfig;
};

function ModifyRsbuildConfig(
  callback: (
    config: RsbuildConfig,
    utils: ModifyRsbuildConfigUtils,
  ) => MaybePromise<RsbuildConfig | void>,
): void;
      • Example: Setting a default value for a specific config option:
      const myPlugin = () => ({
  setup(api) {
    api.modifyRsbuildConfig((config) => {
      config.html ||= {};
      config.html.title = 'My Default Title';
    });
  },
});
      • Example: Using mergeRsbuildConfig to merge config objects, and return the merged object.
      import type { RsbuildConfig } from '@rsbuild/core';

const myPlugin = () => ({
  setup(api) {
    api.modifyRsbuildConfig((userConfig, { mergeRsbuildConfig }) => {
      const extraConfig: RsbuildConfig = {
        source: {
          // ...
        },
        output: {
          // ...
        },
      };

      // extraConfig will override fields in userConfig,
      // If you do not want to override the fields in userConfig,
      // you can adjust to `mergeRsbuildConfig(extraConfig, userConfig)`
      return mergeRsbuildConfig(userConfig, extraConfig);
    });
  },
});
      Tip

      modifyRsbuildConfig cannot be used to register additional Rsbuild plugins. This is because at the time modifyRsbuildConfig is executed, Rsbuild has already initialized all plugins and started executing the callbacks of the hooks.

      For details, please refer to Plugin registration phase.

      modifyEnvironmentConfig

      Modify the Rsbuild configuration of a specific environment.

      In the callback function, the config object in the parameters has already been merged with the common Rsbuild configuration. You can directly modify this config object, or you can return a new object to replace it.

      • Type:
      type ArrayAtLeastOne<A, B> = [A, ...Array<A | B>] | [...Array<A | B>, A];

type ModifyEnvironmentConfigUtils = {
  /** Current environment name */
  name: string;
  mergeEnvironmentConfig: (
    ...configs: ArrayAtLeastOne<MergedEnvironmentConfig, EnvironmentConfig>
  ) => EnvironmentConfig;
};

function ModifyEnvironmentConfig(
  callback: (
    config: EnvironmentConfig,
    utils: ModifyEnvironmentConfigUtils,
  ) => MaybePromise<EnvironmentConfig | void>,
): void;
      • Example: Set a default value for the Rsbuild config of a specified environment:
      const myPlugin = () => ({
  setup(api) {
    api.modifyEnvironmentConfig((config, { name }) => {
      if (name !== 'web') {
        return config;
      }
      config.html.title = 'My Default Title';
    });
  },
});
      • Example: Using mergeEnvironmentConfig to merge config objects, and return the merged object.
      import type { EnvironmentConfig } from '@rsbuild/core';

const myPlugin = () => ({
  setup(api) {
    api.modifyEnvironmentConfig((userConfig, { mergeEnvironmentConfig }) => {
      const extraConfig: EnvironmentConfig = {
        source: {
          // ...
        },
        output: {
          // ...
        },
      };

      // extraConfig will override fields in userConfig,
      // If you do not want to override the fields in userConfig,
      // you can adjust to `mergeEnvironmentConfig(extraConfig, userConfig)`
      return mergeEnvironmentConfig(userConfig, extraConfig);
    });
  },
});

      modifyRspackConfig

      To modify the Rspack config, you can directly modify the config object, or return a new object to replace the previous object.

      Tip

      modifyRspackConfig is executed earlier than tools.rspack. Therefore, the modifications made by tools.rspack cannot be obtained in modifyRspackConfig.

      • Type:
      type ModifyRspackConfigUtils = {
  environment: EnvironmentContext;
  env: string;
  isDev: boolean;
  isProd: boolean;
  target: RsbuildTarget;
  isServer: boolean;
  isWebWorker: boolean;
  rspack: Rspack;
  HtmlPlugin: typeof import('html-rspack-plugin');
  // more...
};

function ModifyRspackConfig(
  callback: (
    config: Rspack.Configuration,
    utils: ModifyRspackConfigUtils,
  ) => Promise<RspackConfig | void> | Rspack.Configuration | void,
): void;
      • Example:
      const myPlugin = () => ({
  setup(api) {
    api.modifyRspackConfig((config, utils) => {
      if (utils.env === 'development') {
        config.devtool = 'eval-cheap-source-map';
      }
    });
  },
});

      The second parameter utils of the callback function is an object, which contains some utility functions and properties, see tools.rspack - Utils for more details.

      modifyBundlerChain

      rspack-chain is a utility library for configuring Rspack. It provides a chaining API, making the configuration of Rspack more flexible. By using rspack-chain, you can more easily modify and extend Rspack configurations without directly manipulating the complex configuration object.

      modifyBundlerChain allows you to modify the Rspack configuration using the rspack-chain API, providing the same functionality as tools.bundlerChain.

      • Type:
      type ModifyBundlerChainUtils = {
  environment: EnvironmentContext;
  env: string;
  isDev: boolean;
  isProd: boolean;
  target: RsbuildTarget;
  isServer: boolean;
  isWebWorker: boolean;
  CHAIN_ID: ChainIdentifier;
  HtmlPlugin: typeof import('html-rspack-plugin');
  bundler: {
    // some Rspack built-in plugins
  };
};

function ModifyBundlerChain(
  callback: (
    chain: RspackChain,
    utils: ModifyBundlerChainUtils,
  ) => Promise<void> | void,
): void;
      • Example:
      import { BundleAnalyzerPlugin } from 'webpack-bundle-analyzer';

const myPlugin = () => ({
  setup(api) {
    api.modifyBundlerChain((chain, utils) => {
      if (utils.env === 'development') {
        chain.devtool('eval');
      }

      chain.plugin('bundle-analyze').use(BundleAnalyzerPlugin);
    });
  },
});

      The second parameter utils of the callback function is an object, which contains some utility functions and properties, see tools.bundlerChain - Utils for more details.

      modifyHTML

      Modify the final HTML content. The hook receives an HTML string and a context object, and you can return a new HTML string to replace the original one.

      This hook is triggered after the modifyHTMLTags hook.

      • Type:
      type Context = {
  /**
   * The Compiler object of Rspack.
   */
  compiler: Rspack.Compiler;
  /**
   * The Compilation object of Rspack.
   */
  compilation: Rspack.Compilation;
  /**
   * The name of the HTML file, relative to the dist directory.
   * @example 'index.html'
   */
  filename: string;
  /**
   * The environment context for current build.
   */
  environment: EnvironmentContext;
};

function ModifyHTML(
  callback: (html: string, context: Context) => MaybePromise<string>,
): void;
      • Version: Added in v1.3.15
      • Example:
      const myPlugin = () => ({
  setup(api) {
    api.modifyHTML((html) => {
      return html.replace('foo', 'bar');
    });
  },
});

      Modify HTML content based on filename:

      const myPlugin = () => ({
  setup(api) {
    api.modifyHTML((html, { filename }) => {
      if (filename === 'foo.html') {
        return html.replace('foo', 'bar');
      }
      return html;
    });
  },
});

      Instead of directly manipulating the HTML string, you can use cheerio or htmlparser2 to modify the HTML content more conveniently.

      For example, cheerio provides a jQuery-like API for HTML manipulation:

      import cheerio from 'cheerio';

const myPlugin = () => ({
  setup(api) {
    api.modifyHTML((html) => {
      const $ = cheerio.load(html);
      $('h2.title').text('Hello there!');
      $('h2').addClass('welcome');
      return $.html();
    });
  },
});

      modifyHTMLTags

      Modify the tags that are injected into the HTML.

      • Type:
      type HtmlBasicTag = {
  // Tag name
  tag: string;
  // Attributes of the tag
  attrs?: Record<string, string | boolean | null | undefined>;
  // innerHTML of the tag
  children?: string;
  // additional metadata
  metadata?: Record<string, any>;
};

type HTMLTags = {
  // Tags group inserted into <head>
  headTags: HtmlBasicTag[];
  // Tags group inserted into <body>
  bodyTags: HtmlBasicTag[];
};

type Context = {
  /**
   * The Compiler object of Rspack.
   */
  compiler: Rspack.Compiler;
  /**
   * The Compilation object of Rspack.
   */
  compilation: Rspack.Compilation;
  /**
   * URL prefix of assets.
   * @example 'https://example.com/'
   */
  assetPrefix: string;
  /**
   * The name of the HTML file, relative to the dist directory.
   * @example 'index.html'
   */
  filename: string;
  /**
   * The environment context for current build.
   */
  environment: EnvironmentContext;
};

function ModifyHTMLTags(
  callback: (tags: HTMLTags, context: Context) => MaybePromise<HTMLTags>,
): void;
      • Example:
      const tagsPlugin = () => ({
  name: 'tags-plugin',
  setup(api) {
    api.modifyHTMLTags(({ headTags, bodyTags }) => {
      // Inject a tag into <head>, before other tags
      headTags.unshift({
        tag: 'script',
        attrs: { src: 'https://example.com/foo.js' },
      });

      // Inject a tag into <head>, after other tags
      headTags.push({
        tag: 'script',
        attrs: { src: 'https://example.com/bar.js' },
      });

      // Inject a tag into <body>, before other tags
      bodyTags.unshift({
        tag: 'div',
        children: 'before other body tags',
      });

      // Inject a tag into <body>, after other tags
      bodyTags.push({
        tag: 'div',
        children: 'after other body tags',
      });

      return { headTags, bodyTags };
    });
  },
});

      See html.tags for more details on how to define tags.

      Tip

      When using modifyHTML, modifyHTMLTags, and html.tags options together, the execution order is as follows:

      1. modifyHTML
      2. modifyHTMLTags
      3. html.tags

      onBeforeCreateCompiler

      A callback function that is triggered after the Compiler instance has been created, but before the build process begins. This hook is called when you run rsbuild.startDevServer, rsbuild.build, or rsbuild.createCompiler.

      You can access the Rspack configuration array through the bundlerConfigs parameter. The array may contain one or more Rspack configurations. It depends on whether multiple environments are configured.

      • Type:
      function OnBeforeCreateCompiler(
  callback: (params: {
    bundlerConfigs: Rspack.Configuration[];
    environments: Record<string, EnvironmentContext>;
  }) => Promise<void> | void,
): void;
      • Example:
      const myPlugin = () => ({
  setup(api) {
    api.onBeforeCreateCompiler(({ bundlerConfigs }) => {
      console.log('the bundler configs are ', bundlerConfigs);
    });
  },
});

      onAfterCreateCompiler

      A callback function that is triggered after the compiler instance has been created, but before the build process. This hook is called when you run rsbuild.startDevServer, rsbuild.build, or rsbuild.createCompiler.

      You can access the Compiler instance through the compiler parameter:

      • Type:
      function OnAfterCreateCompiler(callback: (params: {
  compiler: Compiler | MultiCompiler;
  environments: Record<string, EnvironmentContext>;
}) => Promise<void> | void;): void;
      • Example:
      const myPlugin = () => ({
  setup(api) {
    api.onAfterCreateCompiler(({ compiler }) => {
      console.log('the compiler is ', compiler);
    });
  },
});

      onBeforeEnvironmentCompile

      A callback function that is triggered before the compilation of a single environment.

      You can access the Rspack configuration array through the bundlerConfigs parameter. The array may contain one or more Rspack configurations. It depends on whether multiple environments are configured.

      Moreover, you can use isWatch to determine whether it is dev or build watch mode, and use isFirstCompile to determine whether it is the first build.

      • Type:
      function OnBeforeEnvironmentCompile(
  callback: (params: {
    isWatch: boolean;
    isFirstCompile: boolean;
    bundlerConfig?: Rspack.Configuration;
    environment: EnvironmentContext;
  }) => Promise<void> | void,
): void;
      • Example:
      const myPlugin = () => ({
  setup(api) {
    api.onBeforeEnvironmentCompile(({ bundlerConfig, environment }) => {
      console.log(
        `the bundler config for the ${environment.name} is `,
        bundlerConfig,
      );
    });
  },
});

      onAfterEnvironmentCompile

      A callback function that is triggered after the compilation of a single environment. You can access the build result information via the stats parameter.

      Moreover, you can use isWatch to determine whether it is dev or build watch mode, and use isFirstCompile to determine whether it is the first build.

      • Type:
      function OnAfterEnvironmentCompile(
  callback: (params: {
    isFirstCompile: boolean;
    isWatch: boolean;
    stats?: Stats;
    environment: EnvironmentContext;
    /**
     * The time it takes to build the current environment in milliseconds.
     */
    time: number;
  }) => Promise<void> | void,
): void;
      • Example:
      const myPlugin = () => ({
  setup(api) {
    api.onAfterEnvironmentCompile(({ isFirstCompile, stats }) => {
      console.log(stats?.toJson(), isFirstCompile);
    });
  },
});

      Build hooks

      onBeforeBuild

      A callback function that is triggered before the production build is executed.

      You can access the Rspack configuration array through the bundlerConfigs parameter. The array may contain one or more Rspack configurations. It depends on whether multiple environments are configured.

      Moreover, you can use isWatch to determine whether it is watch mode, and use isFirstCompile to determine whether it is the first build on watch mode.

      • Type:
      function OnBeforeBuild(
  callback: (params: {
    isWatch: boolean;
    isFirstCompile: boolean;
    bundlerConfigs?: Rspack.Configuration[];
    environments: Record<string, EnvironmentContext>;
  }) => Promise<void> | void,
): void;
      • Example:
      const myPlugin = () => ({
  setup(api) {
    api.onBeforeBuild(({ bundlerConfigs }) => {
      console.log('the bundler configs are ', bundlerConfigs);
    });
  },
});

      onAfterBuild

      A callback function that is triggered after running the production build. You can access the build result information via the stats parameter.

      Moreover, you can use isWatch to determine whether it is watch mode, and use isFirstCompile to determine whether it is the first build on watch mode.

      • Type:
      function OnAfterBuild(
  callback: (params: {
    isFirstCompile: boolean;
    isWatch: boolean;
    stats?: Stats | MultiStats;
    environments: Record<string, EnvironmentContext>;
  }) => Promise<void> | void,
): void;
      • Example:
      const myPlugin = () => ({
  setup(api) {
    api.onAfterBuild(({ isFirstCompile, stats }) => {
      console.log(stats?.toJson(), isFirstCompile);
    });
  },
});

      onCloseBuild

      Called when closing the build instance. Can be used to perform cleanup operations when the building is closed.

      Rsbuild CLI will automatically call this hook after running rsbuild build, while users of the JavaScript API need to manually call the build.close() method to trigger this hook.

      • Type:
      function onCloseBuild(callback: () => Promise<void> | void): void;
      • Example:
      const myPlugin = () => ({
  setup(api) {
    api.onCloseBuild(() => {
      console.log('close build!');
    });
  },
});

      Dev hooks

      onBeforeStartDevServer

      Called before starting the dev server.

      Use the server parameter to get the dev server instance, see Dev server API for more information.

      • Type:
      type OnBeforeStartDevServerFn = (params: {
  /**
   * The dev server instance, the same as the return value of `createDevServer`.
   */
  server: RsbuildDevServer;
  /**
   * Context information for all environments.
   */
  environments: Record<string, EnvironmentContext>;
}) => MaybePromise<void>;

function OnBeforeStartDevServer(callback: OnBeforeStartDevServerFn): void;
      • Example:
      const myPlugin = () => ({
  setup(api) {
    api.onBeforeStartDevServer(({ server, environments }) => {
      console.log('before starting dev server.');
      console.log('the server is ', server);
      console.log('the environments contexts are: ', environments);
    });
  },
});

      Register middleware

      A common usage scenario is to register custom middleware in onBeforeStartDevServer:

      const myPlugin = () => ({
  setup(api) {
    api.onBeforeStartDevServer(({ server }) => {
      server.middlewares.use((req, res, next) => {
        next();
      });
    });
  },
});

      When onBeforeStartDevServer is called, the default middleware of Rsbuild are not registered yet, so the middleware you add will run before the default middleware.

      onBeforeStartDevServer allows you to return a callback function, which will be called when the default middleware of Rsbuild are registered. The middleware you register in the callback function will run after the default middleware.

      const myPlugin = () => ({
  setup(api) {
    api.onBeforeStartDevServer(({ server }) => {
      // the returned callback will be called when the default
      // middleware are registered
      return () => {
        server.middlewares.use((req, res, next) => {
          next();
        });
      };
    });
  },
});

      Store server instance

      If you need to access server in other hooks, you can store the server instance through api.onBeforeStartDevServer, and then access it in the hooks executed later. Note that you cannot access server in hooks that are executed earlier than onBeforeStartDevServer.

      import type { RsbuildDevServer } from '@rsbuild/core';

const myPlugin = () => ({
  setup(api) {
    let devServer: RsbuildDevServer | null = null;

    api.onBeforeStartDevServer(({ server, environments }) => {
      devServer = server;
    });

    api.transform({ test: /\.foo$/ }, ({ code }) => {
      if (devServer) {
        // access server API
      }
      return code;
    });

    api.onCloseDevServer(() => {
      devServer = null;
    });
  },
});

      onAfterStartDevServer

      Called after starting the dev server, you can get the port number with the port parameter, and the page routes info with the routes parameter.

      • Type:
      type Routes = Array<{
  entryName: string;
  pathname: string;
}>;

function OnAfterStartDevServer(
  callback: (params: {
    port: number;
    routes: Routes;
    environments: Record<string, EnvironmentContext>;
  }) => Promise<void> | void,
): void;
      • Example:
      const myPlugin = () => ({
  setup(api) {
    api.onAfterStartDevServer(({ port, routes }) => {
      console.log('this port is: ', port);
      console.log('this routes is: ', routes);
    });
  },
});

      onBeforeDevCompile

      A callback function that is triggered before the dev compile is executed.

      You can access the Rspack configuration array through the bundlerConfigs parameter. The array may contain one or more Rspack configurations. It depends on whether multiple environments are configured.

      Moreover, you can use isFirstCompile to determine whether it is the first compile.

      • Type:
      function OnBeforeDevCompile(
  callback: (params: {
    isWatch: boolean;
    isFirstCompile: boolean;
    bundlerConfigs?: Rspack.Configuration[];
    environments: Record<string, EnvironmentContext>;
  }) => Promise<void> | void,
): void;
      • Version: Added in v1.5.0
      • Example:
      const myPlugin = () => ({
  setup(api) {
    api.onBeforeDevCompile(({ bundlerConfigs }) => {
      console.log('the bundler configs are ', bundlerConfigs);
    });
  },
});

      onAfterDevCompile

      Called after each development mode build, you can use isFirstCompile to determine whether it is the first build.

      • Type:
      function OnAfterDevCompile(
  callback: (params: {
    isFirstCompile: boolean;
    stats: Stats | MultiStats;
    environments: Record<string, EnvironmentContext>;
  }) => Promise<void> | void,
): void;
      Tip

      The onAfterDevCompile hook was added in Rsbuild v1.5.0. For earlier versions, you can use the functionally identical onDevCompileDone hook.

      • Example:
      const myPlugin = () => ({
  setup(api) {
    api.onAfterDevCompile(({ isFirstCompile }) => {
      if (isFirstCompile) {
        console.log('first compile!');
      } else {
        console.log('re-compile!');
      }
    });
  },
});

      onCloseDevServer

      Called when closing the dev server. Can be used to perform cleanup operations when the dev server is closed.

      Rsbuild CLI will automatically call this hook at the appropriate time, while users of the JavaScript API need to manually call the server.close() method to trigger this hook.

      • Type:
      function onCloseDevServer(callback: () => Promise<void> | void): void;
      • Example:
      const myPlugin = () => ({
  setup(api) {
    api.onCloseDevServer(async () => {
      console.log('close dev server!');
    });
  },
});

      Preview hooks

      onBeforeStartProdServer

      Called before starting the production preview server.

      • Type:
      function OnBeforeStartProdServer(callback: () => Promise<void> | void): void;
      • Example:
      const myPlugin = () => ({
  setup(api) {
    api.onBeforeStartProdServer(() => {
      console.log('before start!');
    });
  },
});

      onAfterStartProdServer

      Called after starting the production preview server, you can get the port number with the port parameter, and the page routes info with the routes parameter.

      • Type:
      type Routes = Array<{
  entryName: string;
  pathname: string;
}>;

function OnAfterStartProdServer(
  callback: (params: {
    port: number;
    routes: Routes;
    environments: Record<string, EnvironmentContext>;
  }) => Promise<void> | void,
): void;
      • Example:
      const myPlugin = () => ({
  setup(api) {
    api.onAfterStartProdServer(({ port, routes }) => {
      console.log('this port is: ', port);
      console.log('this routes is: ', routes);
    });
  },
});

      Other hooks

      onExit

      Called when the process is going to exit, this hook can only execute synchronous code.

      • Type:
      function OnExit(callback: (context: { exitCode: number }) => void): void;
      • Example:
      const myPlugin = () => ({
  setup(api) {
    api.onExit(({ exitCode }) => {
      console.log('exit: ', exitCode);
    });
  },
});