Nice features

• If you use hashbang like #!/bin/env node in your entry file, tsup will automatically make the output file executable.
• By default tsup doesn’t bundle dependencies and devDependencies, but you can selective bundle them with noExternal option.
• Passing metadata to defineConfig export metadata about the build process for visualize modules size in the bundle. You can pass it to Bundle Size Analyzer
• JSON Schema Store for VSCode

{
  "json.schemas": [
    {
      "url": "https://cdn.jsdelivr.net/npm/tsup/schema.json",
      "fileMatch": ["package.json", "tsup.config.json"]
    }
  ]
}
{
  "json.schemas": [
    {
      "url": "https://cdn.jsdelivr.net/npm/tsup/schema.json",
      "fileMatch": ["package.json", "tsup.config.json"]
    }
  ]
}

Limitations

• Code splitting currently only works with the esm output format (Code splitting is still experimental on ESBuild).
• CSS support is still experimental
• Tree shaking is not perfect, but it’s good enough for most of the cases.
• TypeScript declaration maps (.d.ts.map) are not handled by tsup (https://github.com/egoist/tsup/issues/564).

Results

• Migrating TSUP have improved build time of the projects with a drop of 60% (Thanks ESBuild) 🚀
• Developer experience is improved with a simple configuration and a great watch mode 🤲
• People enjoy the lightness and the semplicity of the configuration file 😄

Bonus

• Using tsup in combination with lerna + nx cache, we have reduced the build time of monorepos by 80% 👨‍🚀