Root Directory

Specify the root directory of input files for output structure mapping.

Overview

The root option is similar to TypeScript's rootDir. It determines how entry file paths map to output paths. By default, tsdown computes the root as the common base directory of all entry files. Setting root explicitly lets you override this behavior.

Basic Usage

CLI

tsdown --root src

Config File

export default defineConfig({
  entry: ['src/index.ts', 'src/utils/helper.ts'],
  root: 'src',
})

How It Works

Default

Given entries src/index.ts and src/utils/helper.ts, the common base directory is src/:

dist/
├── index.js
└── utils/
    └── helper.js

With `root: '.'`

Setting root to the project directory preserves the src/ prefix:

dist/
└── src/
    ├── index.js
    └── utils/
        └── helper.js

What It Affects

Entry name resolution — Array entry paths are computed relative to root for output filenames
Unbundle mode — Used as preserveModulesRoot, controlling output structure when unbundle: true

When to Use

Auto-computed common base directory doesn't produce desired output structure
Need to include or exclude directory prefixes in output paths
Unbundle mode needs specific directory mapping

Common Patterns

Library with `src/` Prefix Preserved

export default defineConfig({
  entry: ['src/**/*.ts', '!**/*.test.ts'],
  root: '.',
  unbundle: true,
})

Monorepo Package

export default defineConfig({
  entry: ['src/index.ts'],
  root: 'src',
  unbundle: true,
})

Unbundle - Preserve directory structure
Entry - Entry point configuration
Output Directory - Output location

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