/tsdown

name: tsdown
description: Bundle TypeScript and JavaScript libraries with blazing-fast speed powered by Rolldown. Use when building libraries, generating type declarations, bundling for multiple formats, or migrating from tsup.

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`](references/option-target.md) 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](references/guide-getting-started.md) | | Configuration File | Config file formats, multiple configs, workspace | [option-config-file](references/option-config-file.md) | | CLI Reference | All CLI commands and options | [reference-cli](references/reference-cli.md) | | Migrate from tsup | Migration guide and compatibility notes | [guide-migrate-from-tsup](references/guide-migrate-from-tsup.md) | | Plugins | Rolldown, Rollup, Unplugin support | [advanced-plugins](references/advanced-plugins.md) |

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

Build Options

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

Dependency Handling

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

Output Enhancement

| Feature | Usage | Reference | |---------|-------|-----------| | Shims | `shims: true` - Add ESM/CJS compatibility | [option-shims](references/option-shims.md) | | CJS default | `cjsDefault: true` (default) / `false` | [option-cjs-default](references/option-cjs-default.md) | | Package exports | `exports: true` - Generate exports field | [option-package-exports](references/option-package-exports.md) | | CSS handling | **[experimental]** `css: { ... }` — full pipeline with preprocessors, Lightning CSS, PostCSS, CSS modules, code splitting; requires `@tsdown/css` | [option-css](references/option-css.md) | | CSS modules | `css: { modules: { localsConvention: 'camelCase' } }` — scoped class names for `.module.css` files | [option-css](references/option-css.md) | | CSS