Rspack Bundler

Rspack-specific configuration for ESBoot.

Rspack is a high-performance Rust-based bundler with strong compatibility with Webpack-style configuration.

Base Config Support

Rspack mode supports the same major ESBoot options as Webpack mode, including:

• server.proxy
• server.https
• server.http2
• server.open
• server.port
• outputPath
• publicPath
• useLangJsonPicker
• minimize
• jsMinifier
• jsMinifierOptions
• cssMinifier
• cssMinifierOptions
• analyze
• alias
• define
• sourceMap
• externals
• copy
• svgr
• svgrOptions
• assetsInlineLimit
• px2rem
• useTailwindcss

Note

Rspack mode currently uses swc_core and browserslist for target configuration.

Base Feature Support

• Compatibility (ES2020+)
• Code splitting

CSS Modules and styleName Support

esboot-bundler-rspack includes a custom WASM plugin, rspack-plugin-stylename, to support styleName in JSX and TSX.

Highlights

• Written in Rust and compiled to WASM
• Converts styleName="foo" into runtime styles[...] lookups
• Includes camelCase fallback for kebab-case CSS class names
• Preserves existing className expressions and combines them correctly

The plugin is enabled automatically when using bundler-rspack.

customConfig

• Type: (config: RspackConfig) => RspackConfig

Use this when ESBoot's higher-level config is not enough and you need direct Rspack control.

export default defineConfig((compileConfig) => {
  return {
    customConfig: (cfg) => {
      return cfg;
    },
  };
});