Notable Features

This page documents some notable features in Rolldown that do not have built-in equivalents in Rollup.

Platform presets

• Configurable via the platform option.
• Default: browser
• Possible values: browser | node | neutral

Similar to esbuild's platform option, this option provides some sensible defaults regarding module resolution and how to handle process.env.NODE_ENV.

Notable differences from esbuild:

• The default output format is always esm regardless of platform.
• No </script> escape behavior when platform is browser.

TIP

Rolldown does not polyfill Node built-ins when targeting the browser. You can opt-in to it with rolldown-plugin-node-polyfills.

Built-in transforms

Rolldown supports the following transforms out of the box, powered by Oxc. The transform is configurable via the transform option. The following transforms are supported:

• TypeScript
  • Sets configurations based on the tsconfig.json when tsconfig option is provided.
  • Supported legacy decorators and decorator metadata.
• JSX
• Syntax lowering
  • Automatically transforms modern syntax to be compatible with your defined target.
  • Supports down to ES2015.

CJS support

Rolldown supports mixed ESM / CJS module graphs out of the box, without the need for @rollup/plugin-commonjs. It largely follows esbuild's semantics and passes all esbuild ESM / CJS interop tests.

See Bundling CJS for more details.

Module resolution

• Configurable via the resolve option
• Powered by oxc-resolver, aligned with webpack's enhanced-resolve

Rolldown resolves modules based on TypeScript and Node.js' behavior by default, without the need for @rollup/plugin-node-resolve.

When top-level tsconfig option is provided, Rolldown will respect compilerOptions.paths in the specified tsconfig.json.

Define

• Configurable via the define option.

This feature provides a way to replace global identifiers with constant expressions. Aligns with the respective options in Vite and esbuild.

@rollup/plugin-replace behaves differently

Note it behaves differently from @rollup/plugin-replace as the replacement is AST-based, so the value to be replaced must be a valid identifier or member expression. Use the built-in replacePlugin for that purpose.

Inject

• Configurable via the inject option.

This feature provides a way to shim global variables with a specific value exported from a module. This feature is equivalent of esbuild's inject option and @rollup/plugin-inject.

CSS bundling

• ⚠️ Experimental

Rolldown supports bundling CSS imported from JS out of the box. Note this feature currently does not support CSS Modules and minification.

Advanced Chunks

• ⚠️ Experimental
• Configurable via output.advancedChunks option.

Rolldown allows controlling the chunking behavior granularly, similar to webpack's optimization.splitChunks feature.

See Advanced Chunks for more details.

Module types

• ⚠️ Experimental

This is conceptually similar to esbuild's loader option, allowing users to globally associate file extensions to built-in module types via the moduleTypes option, or specify module type of a specific module in plugin hooks. It is discussed in more details here.

Minification

• ⚠️ Experimental
• Configurable via the output.minify option.

The minification is powered by oxc-minifier, which is currently in alpha and can still have bugs. We recommend thoroughly testing your output in production environments.

If you prefer an external minifier instead, Rolldown is compatible with Rollup minifier plugins, such as:

rollup-plugin-esbuild:

rolldown.config.js

import { defineConfig } from 'rolldown';
import { minify } from 'rollup-plugin-esbuild';

export default defineConfig({
  plugins: [minify()],
});

rollup-plugin-swc3:

rolldown.config.js

import { defineConfig } from 'rolldown';
import { minify } from 'rollup-plugin-swc3';

export default defineConfig({
  plugins: [
    minify({
      module: true,
      // swc's minify option here
      mangle: {},
      compress: {},
    }),
  ],
});