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tsdown
What tsdown is
tsdown is a free bundler for authors building TypeScript and JavaScript libraries, from small utilities to complex packages. It uses Rolldown, a Rust-based bundler, and can produce ESM, CJS, IIFE, and UMD outputs. It can generate TypeScript declaration files and process JSON and WASM assets. Build features include code splitting, tree shaking, minification, and source maps. tsdown reads package.json and tsconfig.json to infer defaults, including dependency externalization and some declaration settings. Workspace mode detects monorepo packages and inherits root configuration. Plugin support includes Rolldown, many Unplugin plugins, most Rollup plugins, and some Vite plugins; some Rollup plugins may cause TypeScript type errors. Its project describes compatibility with tsup's main options and features to support migration. Installation instructions cover npm, pnpm, Yarn, and Bun, and an online StackBlitz template is available for trying the tool in a browser. Local use requires Node.js ^22.18.0, ^24.11.0, or >=26.0.0; Bun and Deno support is experimental. Executable bundling is also experimental and requires Node.js >=25.7.0. The project is released under the MIT License.
Who it suits
tsdown is aimed at developers publishing TypeScript or JavaScript libraries, from small utilities to complex packages. It may suit authors who want multiple output formats, declaration generation, or monorepo workspace support.
What it does well
- Free plan and MIT License
- Generates TypeScript declaration files
- Supports four output formats
- Online StackBlitz template is available
What to know first
- Local use requires specific Node.js versions
- Bun and Deno support is experimental
- Some Rollup plugins may cause TypeScript type errors
- Executable bundling is experimental
Verdict
tsdown offers library-focused bundling, declaration generation, and plugin support at no charge. Check the specified Node.js requirements and experimental status of Bun, Deno, and executable bundling before choosing it.
Facts from tsdown's own pages
- Assets
- It can include and process non-code assets such as JSON and WASM files. · tsdown.dev, 7 Oct 2026
- Assets and optimization
- It supports JSON and WASM assets, tree shaking, minification, and source maps. · tsdown.dev, 7 Oct 2026
- Build engine
- tsdown is built on Rolldown, a Rust-based bundler. · tsdown.dev, 7 Oct 2026
- Build outputs
- It can produce ESM, CJS, IIFE, and UMD bundles, along with TypeScript declaration files. · tsdown.dev, 7 Oct 2026
- Bundler engine
- tsdown is powered by Rolldown, a Rust-based bundler. · tsdown.dev, 7 Oct 2026
- Configuration
- tsdown reads package.json and tsconfig.json to infer defaults, including dependency externalization and some declaration generation settings. · tsdown.dev, 7 Oct 2026
- Declarations
- tsdown can automatically generate TypeScript declaration files for libraries. · tsdown.dev, 7 Oct 2026
- Experimental executable feature
- Executable bundling is experimental, requires Node.js >=25.7.0, and is not supported in Bun or Deno. · tsdown.dev, 7 Oct 2026
- Install
- The guide provides installation commands for npm, pnpm, Yarn, and Bun. · tsdown.dev, 7 Oct 2026
- Installation
- The getting-started guide documents installation through npm, pnpm, yarn, and Bun. · tsdown.dev, 7 Oct 2026
- Integrations
- The project says it supports Rolldown, Unplugin, and most Rollup plugins, as well as some Vite plugins. · tsdown.dev, 7 Oct 2026
- Intended users
- The documentation describes tsdown as a tool for library authors, from small utilities to complex libraries. · tsdown.dev, 7 Oct 2026
- License
- The project website states that tsdown is released under the MIT License. · tsdown.dev, 7 Oct 2026
- Maker
- The project credits VoidZero Inc. and contributors. · tsdown.dev, 7 Oct 2026
- Migration
- The homepage says tsdown is compatible with tsup's main options and features to support migration. · tsdown.dev, 7 Oct 2026
- Monorepos
- It has workspace mode for detecting monorepo packages and inheriting root configuration. · tsdown.dev, 7 Oct 2026
- Optimization
- Built-in production features include tree-shaking, minification, and source maps. · tsdown.dev, 7 Oct 2026
- Output formats
- It supports ESM, CJS, IIFE, and UMD output formats. · tsdown.dev, 7 Oct 2026
- Plugins
- It supports Rolldown plugins, most Rollup plugins, and many Unplugin plugins; some Rollup plugins may cause TypeScript type errors. · tsdown.dev, 7 Oct 2026
- Purpose
- tsdown is a bundler designed for building TypeScript and JavaScript libraries. · tsdown.dev, 7 Oct 2026
- Runtime requirement
- The guide requires Node.js ^22.18.0, ^24.11.0, or >=26.0.0 to run tsdown and says Bun and Deno support is experimental. · tsdown.dev, 7 Oct 2026
- Security and compliance
- The opened tsdown pages did not state security certifications or compliance claims. · tsdown.dev, 7 Oct 2026
- Try online
- The getting-started guide offers an online StackBlitz template for trying tsdown in a browser without local setup. · tsdown.dev, 7 Oct 2026
Where tsdown stands on Freedom251
- JavaScript Build Tools#27 of 27