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() returns a TsdownHandle. Its bundles array contains one bundle for each resolved configuration. In watch mode, watch.restart() restarts the build and resolves to the new handle, while watch.close() gracefully closes all watchers. Each handle can only be restarted once. Even a single configuration produces 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.