moeka-project/.agents/skills/tsdown/references/guide-introduction.md

Introduction

tsdown is The Elegant Library Bundler — a fast, simple bundler for TypeScript and JavaScript libraries powered by Rolldown (Rust-based).

Why tsdown?

Built on Rolldown, tsdown provides a complete out-of-the-box solution for library authors:

• Simplified Configuration: Sensible defaults for library development, minimal boilerplate
• Library-Specific Features: Auto TypeScript declarations, multiple output formats, package validation
• Future-Ready: Official Rolldown project, foundation for Rolldown Vite's Library Mode

Plugin Ecosystem

Supports the full Rolldown plugin ecosystem plus most Rollup plugins. See Plugins.

What Can It Bundle?

• TypeScript/JavaScript: .ts, .js with modern syntax
• TypeScript Declarations: Auto-generate .d.ts files
• Multiple Formats: esm, cjs, iife, umd
• Assets: .json, .wasm, CSS files
• Built-in tree shaking, minification, and source maps

Key Differences from Rolldown

tsdown wraps Rolldown with library-specific features:

• Auto-external dependencies, peerDependencies, and optionalDependencies from package.json
• DTS generation
• package.json exports field generation
• Watch mode with keyboard shortcuts
• CSS preprocessing pipeline
• Executable bundling (SEA)

Prior Arts

Inspired by: Rollup, esbuild, tsup, unbuild. Powered by Rolldown.

Related

• Getting Started - Installation and first build
• Migrate from tsup - Migration guide