Programmatic Usage

You can use tsdown directly from your JavaScript or TypeScript code. This is useful for custom build scripts, integrations, or advanced automation.

Example

import { build } from 'tsdown'

await build({
  entry: ['src/index.ts'],
  format: ['esm', 'cjs'],
  outDir: 'dist',
  dts: true,
  // ...any other options
})

In-Memory Output

Set write: false to access generated chunks and assets without writing the bundle output to disk:

import { build } from 'tsdown'

const bundles = await build({
  entry: ['src/index.ts'],
  format: 'esm',
  write: false,
  clean: false,
})

for (const bundle of bundles) {
  for (const output of bundle.chunks) {
    const contents = output.type === 'chunk' ? output.code : output.source
    console.log(output.fileName, contents)
  }
}

build() currently returns a TsdownBundle[], with one bundle for each resolved configuration. Even a single configuration returns an array; its in-memory Rolldown outputs are available in bundle.chunks.

The write option controls Rolldown's bundle output, while other file operations are configured separately. For example, clean defaults to true, so set clean: false as above if existing output directories must remain untouched. Explicitly enabled features such as copy or exports may still write files. write: false is incompatible with watch mode.

All CLI options are available as properties in the options object. See Config Options for the full list.