tsdown is a next-generation TypeScript library bundler built on Rolldown and Oxc. It provides blazing-fast builds, automatic .d.ts generation, and seamless migration from tsup. Supports Rolldown/Rollup/Unplugin plugins and features smart dependency handling.

The skill is based on tsdown v0.20.1, generated at 2026-01-28.

Anthony's Preferences:

• Build pure-ESM packages, avoid CJS

• Always enable dts option for type declarations

• Enable exports option for auto-generated package exports

Core

Topic Description Reference

Configuration Config file setup, defineConfig, multiple configs core-config

CLI Command-line interface and options core-cli

Entry Points Entry files, aliases, glob patterns core-entry

Build Options

Topic Description Reference

Output Format (ESM/CJS/IIFE/UMD), directory, target, platform options-output

Declaration Files .d.ts generation, isolatedDeclarations, sourcemaps options-dts

Dependencies External, noExternal, dependency bundling options-dependencies

Package Exports Auto-generating exports, main, module fields options-package-exports

Features

Topic Description Reference

Optimization Tree shaking, minification, sourcemaps features-optimization

Shims CJS/ESM compatibility shims features-shims

Unbundle Mode Bundleless transpile-only builds features-unbundle

Watch Mode Auto-rebuild on file changes features-watch

Advanced

Topic Description Reference

Plugins Rolldown, Unplugin, Rollup, Vite plugins advanced-plugins

Hooks Build lifecycle hooks advanced-hooks

Programmatic API Using tsdown from code advanced-programmatic

Rolldown Options Customizing inputOptions and outputOptions advanced-rolldown-options

Recipes

Topic Description Reference

Framework Support Vue and React library bundling recipes-frameworks

Migration Migrating from tsup recipes-migration