tsdown

tsdown - The Elegant Library Bundler

Blazing-fast bundler for TypeScript/JavaScript libraries powered by Rolldown and Oxc.

Runtime Requirement

tsdown requires Node.js 22.18.0 or higher to run (build-time only). However, the bundled output can target much lower Node.js versions via the target option, so libraries built with tsdown are not locked to Node.js 22+ at runtime.

If your package needs to support Node.js 18 / 20:

Build with Node.js 22+ in CI (e.g. set target: 'node18' or target: 'node20').
Test the built output (or the packed tarball) on the lower Node.js versions you intend to support — e.g. using a matrix job that runs the published package's tests on Node.js 18 / 20 / 22.

When to Use

Building TypeScript/JavaScript libraries for npm
Generating TypeScript declaration files (.d.ts)
Bundling for multiple formats (ESM, CJS, IIFE, UMD)
Optimizing bundles with tree shaking and minification
Migrating from tsup with minimal changes
Building React, Vue, Solid, or Svelte component libraries

Quick Start

# Install
pnpm add -D tsdown
 
# Basic usage
npx tsdown
 
# With config file
npx tsdown --config tsdown.config.ts
 
# Watch mode
npx tsdown --watch
 
# Migrate from tsup
npx tsdown-migrate

Basic Configuration

import { defineConfig } from 'tsdown'
 
export default defineConfig({
  entry: ['./src/index.ts'],
  format: ['esm', 'cjs'],
  dts: true,
  clean: true,
})

Core References

Topic	Description	Reference
Getting Started	Installation, first bundle, CLI basics	guide-getting-started
Configuration File	Config file formats, multiple configs, workspace	option-config-file
CLI Reference	All CLI commands and options	reference-cli
Migrate from tsup	Migration guide and compatibility notes	guide-migrate-from-tsup
Plugins	Rolldown, Rollup, Unplugin support	advanced-plugins

For comprehensive migration assistance with complete option mappings, install the dedicated tsdown-migrate skill: npx skills add rolldown/tsdown --skill tsdown-migrate | Hooks | Lifecycle hooks for custom logic | advanced-hooks | | Programmatic API | Build from Node.js scripts | advanced-programmatic | | Rolldown Options | Pass options directly to Rolldown | advanced-rolldown-options | | CI Environment | CI detection, 'ci-only' / 'local-only' values | advanced-ci |

Build Options

Option	Usage	Reference
Entry points	`entry: ['src/.ts', '!/.test.ts']`	option-entry
Output formats	`format: ['esm', 'cjs', 'iife', 'umd']`	option-output-format
Output directory	`outDir: 'dist'`, `outExtensions`	option-output-directory
Type declarations	`dts: true`, `dts: { sourcemap, compilerOptions, vue }`	option-dts
Target environment	`target: 'es2020'`, `target: 'esnext'`	option-target
Platform	`platform: 'node'`, `platform: 'browser'`	option-platform
Tree shaking	`treeshake: true`, custom options	option-tree-shaking
Minification	`minify: true`, `minify: 'dce-only'`	option-minification
Source maps	`sourcemap: true`, `'inline'`, `'hidden'`	option-sourcemap
Watch mode	`watch: true`, watch options	option-watch-mode
Cleaning	`clean: true`, clean patterns	option-cleaning
Log level	`logLevel: 'silent'`, `failOnWarn: false`	option-log-level

Dependency Handling

Feature	Usage	Reference
Never bundle	`deps: { neverBundle: ['react', /^@myorg\//] }`	option-dependencies
Always bundle	`deps: { alwaysBundle: ['dep-to-bundle'] }`	option-dependencies
Only bundle	`deps: { onlyBundle: ['cac', 'bumpp'] }` - Whitelist	option-dependencies
Skip node_modules	`deps: { skipNodeModulesBundle: true }`	option-dependencies
Auto external	Automatic dependency/peer/optional externalization	option-dependencies

Output Enhancement

Feature	Usage	Reference
Shims	`shims: true` - Add ESM/CJS compatibility	option-shims
CJS default	`cjsDefault: true` (default) / `false`	option-cjs-default
Package exports	`exports: true` - Generate exports field	option-package-exports
CSS handling	[experimental] `css: { ... }` — full pipeline with preprocessors, Lightning CSS, PostCSS, CSS modules, code splitting; requires `@tsdown/css`	option-css
CSS modules	`css: { modules: { localsConvention: 'camelCase' } }` — scoped class names for `.module.css` files	option-css
CSS inject	`css: { inject: true }` — preserve CSS imports in JS output	option-css
Unbundle mode	`unbundle: true` - Preserve directory structure	option-unbundle
Root directory	`root: 'src'` - Control output directory mapping	option-root
Executable	[experimental] `exe: true` - Bundle as standalone executable, cross-platform via `@tsdown/exe`	option-exe
Package validation	`publint: true`, `attw: true` - Validate package	option-lint

Framework & Runtime Support

Framework	Guide	Reference
React	JSX transform, React Compiler	recipe-react
Vue	SFC support, JSX	recipe-vue
Solid	SolidJS JSX transform	recipe-solid
Svelte	Svelte component libraries (source distribution recommended)	recipe-svelte
WASM	WebAssembly modules via `rolldown-plugin-wasm`	recipe-wasm

Common Patterns

Basic Library Bundle

export default defineConfig({
  entry: ['src/index.ts'],
  format: ['esm', 'cjs'],
  dts: true,
  clean: true,
})

Multiple Entry Points

export default defineConfig({
  entry: {
    index: 'src/index.ts',
    utils: 'src/utils.ts',
    cli: 'src/cli.ts',
  },
  format: ['esm', 'cjs'],
  dts: true,
})

Browser Library (IIFE/UMD)

export default defineConfig({
  entry: ['src/index.ts'],
  format: ['iife'],
  globalName: 'MyLib',
  platform: 'browser',
  minify: true,
})

React Component Library

export default defineConfig({
  entry: ['src/index.tsx'],
  format: ['esm', 'cjs'],
  dts: true,
  deps: {
    neverBundle: ['react', 'react-dom'],
  },
  inputOptions: {
    jsx: { runtime: 'automatic' },
  },
})

Preserve Directory Structure

export default defineConfig({
  entry: ['src/**/*.ts', '!**/*.test.ts'],
  unbundle: true, // Preserve file structure
  format: ['esm'],
  dts: true,
})

CI-Aware Configuration

export default defineConfig({
  entry: ['src/index.ts'],
  format: ['esm', 'cjs'],
  dts: true,
  failOnWarn: 'ci-only',  // opt-in: fail on warnings in CI
  publint: 'ci-only',
  attw: 'ci-only',
})

WASM Support

import { wasm } from 'rolldown-plugin-wasm'
import { defineConfig } from 'tsdown'
 
export default defineConfig({
  entry: ['src/index.ts'],
  plugins: [wasm()],
})

Library with CSS and Sass

export default defineConfig({
  entry: ['src/index.ts'],
  format: ['esm', 'cjs'],
  dts: true,
  target: 'chrome100',
  css: {
    preprocessorOptions: {
      scss: {
        additionalData: `@use "src/styles/variables" as *;`,
      },
    },
  },
})

Standalone Executable

export default defineConfig({
  entry: ['src/cli.ts'],
  exe: true,
})

Cross-Platform Executable (requires `@tsdown/exe`)

export default defineConfig({
  entry: ['src/cli.ts'],
  exe: {
    targets: [
      { platform: 'linux', arch: 'x64', nodeVersion: '25.7.0' },
      { platform: 'darwin', arch: 'arm64', nodeVersion: '25.7.0' },
      { platform: 'win', arch: 'x64', nodeVersion: '25.7.0' },
    ],
  },
})

Advanced with Hooks

export default defineConfig({
  entry: ['src/index.ts'],
  format: ['esm', 'cjs'],
  dts: true,
  hooks: {
    'build:before': async (context) => {
      console.log('Building...')
    },
    'build:done': async (context) => {
      console.log('Build complete!')
    },
  },
})

Configuration Features

Multiple Configs

Export an array for multiple build configurations:

export default defineConfig([
  {
    entry: ['src/index.ts'],
    format: ['esm', 'cjs'],
    dts: true,
  },
  {
    entry: ['src/cli.ts'],
    format: ['esm'],
    platform: 'node',
  },
])

Conditional Config

Use functions for dynamic configuration:

export default defineConfig((options) => {
  const isDev = options.watch
  return {
    entry: ['src/index.ts'],
    format: ['esm', 'cjs'],
    minify: !isDev,
    sourcemap: isDev,
  }
})

Workspace/Monorepo

Use glob patterns to build multiple packages:

export default defineConfig({
  workspace: 'packages/*',
  entry: ['src/index.ts'],
  format: ['esm', 'cjs'],
  dts: true,
})

CLI Quick Reference

# Basic commands
tsdown                          # Build once
tsdown --watch                  # Watch mode
tsdown --config custom.ts       # Custom config
npx tsdown-migrate              # Migrate from tsup
 
# Output options
tsdown --format esm,cjs        # Multiple formats
tsdown -d lib                  # Custom output directory (--out-dir)
tsdown --minify                # Enable minification
tsdown --dts                   # Generate declarations
tsdown --exe                   # Bundle as standalone executable
tsdown --unbundle              # Bundleless mode
 
# Entry options
tsdown src/index.ts            # Single entry
tsdown src/*.ts                # Glob patterns
tsdown src/a.ts src/b.ts       # Multiple entries
 
# Workspace / Monorepo
tsdown -W                      # Enable workspace mode
tsdown -W -F my-package        # Filter specific package
tsdown --filter /^pkg-/        # Filter by regex
 
# Development
tsdown --watch                 # Watch mode
tsdown --sourcemap             # Generate source maps
tsdown --clean                 # Clean output directory
tsdown --from-vite             # Reuse Vite config
tsdown --tsconfig tsconfig.build.json  # Custom tsconfig

Best Practices

Always generate type declarations for TypeScript libraries:
```
{ dts: true }
```
Externalize dependencies to avoid bundling unnecessary code:
```
{ deps: { neverBundle: [/^react/, /^@myorg\//] } }
```
Use tree shaking for optimal bundle size:
```
{ treeshake: true }
```
Enable minification for production builds:
```
{ minify: true }
```

Add shims for better ESM/CJS compatibility:

{ shims: true }  // Adds __dirname, __filename, etc.

Auto-generate package.json exports:

{ exports: true }  // Creates proper exports field

Use watch mode during development:
```
tsdown --watch
```
Preserve structure for utilities with many files:
```
{ unbundle: true }  // Keep directory structure
```
Validate packages in CI before publishing:
```
{ publint: 'ci-only', attw: 'ci-only' }
```

Resources

Documentation: https://tsdown.dev
GitHub: https://github.com/rolldown/tsdown
Rolldown: https://rolldown.rs
Migration Guide: https://tsdown.dev/guide/migrate-from-tsup**

tsdown - The Elegant Library Bundler

Blazing-fast bundler for TypeScript/JavaScript libraries powered by Rolldown and Oxc.

Runtime Requirement

If your package needs to support Node.js 18 / 20:

Build with Node.js 22+ in CI (e.g. set target: 'node18' or target: 'node20').
Test the built output (or the packed tarball) on the lower Node.js versions you intend to support — e.g. using a matrix job that runs the published package's tests on Node.js 18 / 20 / 22.

When to Use

Building TypeScript/JavaScript libraries for npm
Generating TypeScript declaration files (.d.ts)
Bundling for multiple formats (ESM, CJS, IIFE, UMD)
Optimizing bundles with tree shaking and minification
Migrating from tsup with minimal changes
Building React, Vue, Solid, or Svelte component libraries

Quick Start

# Install
pnpm add -D tsdown
 
# Basic usage
npx tsdown
 
# With config file
npx tsdown --config tsdown.config.ts
 
# Watch mode
npx tsdown --watch
 
# Migrate from tsup
npx tsdown-migrate

Basic Configuration

import { defineConfig } from 'tsdown'
 
export default defineConfig({
  entry: ['./src/index.ts'],
  format: ['esm', 'cjs'],
  dts: true,
  clean: true,
})

Core References

Topic	Description	Reference
Getting Started	Installation, first bundle, CLI basics	guide-getting-started
Configuration File	Config file formats, multiple configs, workspace	option-config-file
CLI Reference	All CLI commands and options	reference-cli
Migrate from tsup	Migration guide and compatibility notes	guide-migrate-from-tsup
Plugins	Rolldown, Rollup, Unplugin support	advanced-plugins

For comprehensive migration assistance with complete option mappings, install the dedicated tsdown-migrate skill: npx skills add rolldown/tsdown --skill tsdown-migrate | Hooks | Lifecycle hooks for custom logic | advanced-hooks | | Programmatic API | Build from Node.js scripts | advanced-programmatic | | Rolldown Options | Pass options directly to Rolldown | advanced-rolldown-options | | CI Environment | CI detection, 'ci-only' / 'local-only' values | advanced-ci |

Build Options

Option	Usage	Reference
Entry points	`entry: ['src/.ts', '!/.test.ts']`	option-entry
Output formats	`format: ['esm', 'cjs', 'iife', 'umd']`	option-output-format
Output directory	`outDir: 'dist'`, `outExtensions`	option-output-directory
Type declarations	`dts: true`, `dts: { sourcemap, compilerOptions, vue }`	option-dts
Target environment	`target: 'es2020'`, `target: 'esnext'`	option-target
Platform	`platform: 'node'`, `platform: 'browser'`	option-platform
Tree shaking	`treeshake: true`, custom options	option-tree-shaking
Minification	`minify: true`, `minify: 'dce-only'`	option-minification
Source maps	`sourcemap: true`, `'inline'`, `'hidden'`	option-sourcemap
Watch mode	`watch: true`, watch options	option-watch-mode
Cleaning	`clean: true`, clean patterns	option-cleaning
Log level	`logLevel: 'silent'`, `failOnWarn: false`	option-log-level

Dependency Handling

Feature	Usage	Reference
Never bundle	`deps: { neverBundle: ['react', /^@myorg\//] }`	option-dependencies
Always bundle	`deps: { alwaysBundle: ['dep-to-bundle'] }`	option-dependencies
Only bundle	`deps: { onlyBundle: ['cac', 'bumpp'] }` - Whitelist	option-dependencies
Skip node_modules	`deps: { skipNodeModulesBundle: true }`	option-dependencies
Auto external	Automatic dependency/peer/optional externalization	option-dependencies

Output Enhancement

Feature	Usage	Reference
Shims	`shims: true` - Add ESM/CJS compatibility	option-shims
CJS default	`cjsDefault: true` (default) / `false`	option-cjs-default
Package exports	`exports: true` - Generate exports field	option-package-exports
CSS handling	[experimental] `css: { ... }` — full pipeline with preprocessors, Lightning CSS, PostCSS, CSS modules, code splitting; requires `@tsdown/css`	option-css
CSS modules	`css: { modules: { localsConvention: 'camelCase' } }` — scoped class names for `.module.css` files	option-css
CSS inject	`css: { inject: true }` — preserve CSS imports in JS output	option-css
Unbundle mode	`unbundle: true` - Preserve directory structure	option-unbundle
Root directory	`root: 'src'` - Control output directory mapping	option-root
Executable	[experimental] `exe: true` - Bundle as standalone executable, cross-platform via `@tsdown/exe`	option-exe
Package validation	`publint: true`, `attw: true` - Validate package	option-lint

Framework & Runtime Support

Framework	Guide	Reference
React	JSX transform, React Compiler	recipe-react
Vue	SFC support, JSX	recipe-vue
Solid	SolidJS JSX transform	recipe-solid
Svelte	Svelte component libraries (source distribution recommended)	recipe-svelte
WASM	WebAssembly modules via `rolldown-plugin-wasm`	recipe-wasm

Common Patterns

Basic Library Bundle

export default defineConfig({
  entry: ['src/index.ts'],
  format: ['esm', 'cjs'],
  dts: true,
  clean: true,
})

Multiple Entry Points

export default defineConfig({
  entry: {
    index: 'src/index.ts',
    utils: 'src/utils.ts',
    cli: 'src/cli.ts',
  },
  format: ['esm', 'cjs'],
  dts: true,
})

Browser Library (IIFE/UMD)

export default defineConfig({
  entry: ['src/index.ts'],
  format: ['iife'],
  globalName: 'MyLib',
  platform: 'browser',
  minify: true,
})

React Component Library

export default defineConfig({
  entry: ['src/index.tsx'],
  format: ['esm', 'cjs'],
  dts: true,
  deps: {
    neverBundle: ['react', 'react-dom'],
  },
  inputOptions: {
    jsx: { runtime: 'automatic' },
  },
})

Preserve Directory Structure

export default defineConfig({
  entry: ['src/**/*.ts', '!**/*.test.ts'],
  unbundle: true, // Preserve file structure
  format: ['esm'],
  dts: true,
})

CI-Aware Configuration

export default defineConfig({
  entry: ['src/index.ts'],
  format: ['esm', 'cjs'],
  dts: true,
  failOnWarn: 'ci-only',  // opt-in: fail on warnings in CI
  publint: 'ci-only',
  attw: 'ci-only',
})

WASM Support

import { wasm } from 'rolldown-plugin-wasm'
import { defineConfig } from 'tsdown'
 
export default defineConfig({
  entry: ['src/index.ts'],
  plugins: [wasm()],
})

Library with CSS and Sass

export default defineConfig({
  entry: ['src/index.ts'],
  format: ['esm', 'cjs'],
  dts: true,
  target: 'chrome100',
  css: {
    preprocessorOptions: {
      scss: {
        additionalData: `@use "src/styles/variables" as *;`,
      },
    },
  },
})

Standalone Executable

export default defineConfig({
  entry: ['src/cli.ts'],
  exe: true,
})

Cross-Platform Executable (requires `@tsdown/exe`)

export default defineConfig({
  entry: ['src/cli.ts'],
  exe: {
    targets: [
      { platform: 'linux', arch: 'x64', nodeVersion: '25.7.0' },
      { platform: 'darwin', arch: 'arm64', nodeVersion: '25.7.0' },
      { platform: 'win', arch: 'x64', nodeVersion: '25.7.0' },
    ],
  },
})

Advanced with Hooks

export default defineConfig({
  entry: ['src/index.ts'],
  format: ['esm', 'cjs'],
  dts: true,
  hooks: {
    'build:before': async (context) => {
      console.log('Building...')
    },
    'build:done': async (context) => {
      console.log('Build complete!')
    },
  },
})

Configuration Features

Multiple Configs

Export an array for multiple build configurations:

export default defineConfig([
  {
    entry: ['src/index.ts'],
    format: ['esm', 'cjs'],
    dts: true,
  },
  {
    entry: ['src/cli.ts'],
    format: ['esm'],
    platform: 'node',
  },
])

Conditional Config

Use functions for dynamic configuration:

export default defineConfig((options) => {
  const isDev = options.watch
  return {
    entry: ['src/index.ts'],
    format: ['esm', 'cjs'],
    minify: !isDev,
    sourcemap: isDev,
  }
})

Workspace/Monorepo

Use glob patterns to build multiple packages:

export default defineConfig({
  workspace: 'packages/*',
  entry: ['src/index.ts'],
  format: ['esm', 'cjs'],
  dts: true,
})

CLI Quick Reference

# Basic commands
tsdown                          # Build once
tsdown --watch                  # Watch mode
tsdown --config custom.ts       # Custom config
npx tsdown-migrate              # Migrate from tsup
 
# Output options
tsdown --format esm,cjs        # Multiple formats
tsdown -d lib                  # Custom output directory (--out-dir)
tsdown --minify                # Enable minification
tsdown --dts                   # Generate declarations
tsdown --exe                   # Bundle as standalone executable
tsdown --unbundle              # Bundleless mode
 
# Entry options
tsdown src/index.ts            # Single entry
tsdown src/*.ts                # Glob patterns
tsdown src/a.ts src/b.ts       # Multiple entries
 
# Workspace / Monorepo
tsdown -W                      # Enable workspace mode
tsdown -W -F my-package        # Filter specific package
tsdown --filter /^pkg-/        # Filter by regex
 
# Development
tsdown --watch                 # Watch mode
tsdown --sourcemap             # Generate source maps
tsdown --clean                 # Clean output directory
tsdown --from-vite             # Reuse Vite config
tsdown --tsconfig tsconfig.build.json  # Custom tsconfig

Best Practices

Always generate type declarations for TypeScript libraries:
```
{ dts: true }
```
Externalize dependencies to avoid bundling unnecessary code:
```
{ deps: { neverBundle: [/^react/, /^@myorg\//] } }
```
Use tree shaking for optimal bundle size:
```
{ treeshake: true }
```
Enable minification for production builds:
```
{ minify: true }
```

Add shims for better ESM/CJS compatibility:

{ shims: true }  // Adds __dirname, __filename, etc.

Auto-generate package.json exports:

{ exports: true }  // Creates proper exports field

Use watch mode during development:
```
tsdown --watch
```
Preserve structure for utilities with many files:
```
{ unbundle: true }  // Keep directory structure
```
Validate packages in CI before publishing:
```
{ publint: 'ci-only', attw: 'ci-only' }
```

Resources

Documentation: https://tsdown.dev
GitHub: https://github.com/rolldown/tsdown
Rolldown: https://rolldown.rs
Migration Guide: https://tsdown.dev/guide/migrate-from-tsup**

tsdown

tsdown - The Elegant Library Bundler

Runtime Requirement

When to Use

Quick Start

Basic Configuration

Core References

Build Options

Dependency Handling

Output Enhancement

Framework & Runtime Support

Common Patterns

Basic Library Bundle

Multiple Entry Points

Browser Library (IIFE/UMD)

React Component Library

Preserve Directory Structure

CI-Aware Configuration

WASM Support

Library with CSS and Sass

Standalone Executable

Cross-Platform Executable (requires @tsdown/exe)

Advanced with Hooks

Configuration Features

Multiple Configs

Conditional Config

Workspace/Monorepo

CLI Quick Reference

Best Practices

Resources

tsdown - The Elegant Library Bundler

Runtime Requirement

When to Use

Quick Start

Basic Configuration

Core References

Build Options

Dependency Handling

Output Enhancement

Framework & Runtime Support

Common Patterns

Basic Library Bundle

Multiple Entry Points

Browser Library (IIFE/UMD)

React Component Library

Preserve Directory Structure

CI-Aware Configuration

WASM Support

Library with CSS and Sass

Standalone Executable

Cross-Platform Executable (requires @tsdown/exe)

Advanced with Hooks

Configuration Features

Multiple Configs

Conditional Config

Workspace/Monorepo

CLI Quick Reference

Best Practices

Resources

Cross-Platform Executable (requires `@tsdown/exe`)

Cross-Platform Executable (requires `@tsdown/exe`)