tsdown

Bundle TypeScript and JavaScript libraries into esm, cjs, iife, and umd formats.

Updated Feb 12, 2026

Search Tags:#typescript #library #monorepo #bundling #dts #rolldown

Ready to run

npx skills add https://github.com/christopher-buss/rbxts-transformer-jest --skill tsdown-christopher-buss

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Please help me install this Agent Skill.
Skill: tsdown
Source: https://github.com/christopher-buss/rbxts-transformer-jest/tree/main/.agents/skills/tsdown
Command: npx skills add https://github.com/christopher-buss/rbxts-transformer-jest --skill tsdown-christopher-buss

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

Bundling TypeScript and JavaScript libraries across multiple formats can be tedious and error-prone, especially when generating type declarations and migrating from other tools.

Core Features & Use Cases

Multi-format bundles (esm, cjs, iife, umd) for npm publishing
DTS generation and type declaration support
Monorepo/workspace friendly builds and migration scenarios from tsup

Quick Start

Install tsdown and run a build to generate multi-format bundles for your library.

Frequently Asked Questions about tsdown

High-intent search queries and answers about installing and using this skill.

FAQPage Schema

How do I bundle a TypeScript library into multiple formats like ESM and CJS?▼

Multi-format bundling for TypeScript libraries is automated by generating esm, cjs, iife, and umd outputs for npm publishing. This handles library building and DTS generation to streamline the process.

Does tsdown support monorepo workspace builds for TypeScript libraries?▼

Monorepo workspace builds are natively supported for TypeScript libraries. This allows you to manage library building, DTS generation, and cleaning across multiple packages within a single workspace environment.

Can I migrate my TypeScript library builds from tsup to tsdown?▼

Migration from tsup is explicitly supported for TypeScript library builds. You can transition your existing configuration to automate multi-format outputs, DTS generation, and workspace builds across your monorepo.

What is the best way to generate type declarations when bundling a TS library?▼

Generating type declarations during TS library bundling is handled through integrated DTS generation. This ensures your multi-format bundles include the necessary dts files for npm publishing alongside the esm and cjs outputs.

How do I set up watch mode for TypeScript library bundling?▼

Watch mode for TypeScript library bundling is supported to automate rebuilding your multi-format outputs during development. This allows continuous generation of esm, cjs, and DTS files as source changes.