Migrate from tsup

tsup is a powerful and widely-used bundler that shares many similarities with tsdown. While tsup is built on top of esbuild, tsdown leverages the power of Rolldown to deliver a faster and more powerful bundling experience.

Migration Guide

If you're currently using tsup and want to migrate to tsdown, the process is straightforward thanks to the dedicated migrate command:

npx tsdown-migrate

For monorepos, you can specify directories using glob patterns:

npx tsdown-migrate packages/*

Or specify multiple directories explicitly:

npx tsdown-migrate packages/foo packages/bar

WARNING

Please save your changes before migration. The migration process may modify your configuration files, so it's important to ensure all your changes are committed or backed up beforehand.

TIP

The migration tool will automatically install dependencies after migration. Make sure to run the command from within your project directory.

Migration Options

The migrate command supports the following options to customize the migration process:

• [...dirs]: Specify directories to migrate. Supports glob patterns (e.g., packages/*). Defaults to the current directory if not specified.
• --dry-run (or -d): Perform a dry run to preview the migration without making any changes.

With these options, you can easily tailor the migration process to fit your specific project setup.

Differences from tsup

While tsdown aims to be highly compatible with tsup, there are some differences to be aware of:

Default Values

• format: Defaults to esm.
• clean: Enabled by default and will clean the outDir before each build.
• dts: Automatically enabled if your package.json contains a typings or types field.
• target: By default, reads from the engines.node field in your package.json if available.

Feature Gaps

Some features available in tsup are not yet implemented in tsdown. If you find an option missing that you need, please open an issue to let us know your requirements.

New Features in tsdown

tsdown also introduces new features not available in tsup:

• nodeProtocol: Control how Node.js built-in module imports are handled:
  • true: Add node: prefix to built-in modules (e.g., fs → node:fs)
  • 'strip': Remove node: prefix from imports (e.g., node:fs → fs)
  • false: Keep imports as-is (default)

Please review your configuration after migration to ensure it matches your expectations.

Acknowledgements

tsdown would not have been possible without the inspiration and contributions of the open-source community. We would like to express our heartfelt gratitude to the following:

• tsup: tsdown was heavily inspired by tsup, and even incorporates parts of its codebase. The simplicity and efficiency of tsup served as a guiding light during the development of tsdown.
• @egoist: The creator of tsup, whose work has significantly influenced the JavaScript and TypeScript tooling ecosystem. Thank you for your dedication and contributions to the community.