> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/vitejs/vite/llms.txt
> Use this file to discover all available pages before exploring further.

# Worker Options

> Configuration options for Web Workers in Vite, including output format, plugins, and Rolldown options.

Unless noted, the options in this section are applied to all dev, build, and preview.

## worker.format

* **Type:** `'es' | 'iife'`
* **Default:** `'iife'`

Output format for worker bundle.

## worker.plugins

* **Type:** [`() => (Plugin | Plugin[])[]`](./shared-options#plugins)

Vite plugins that apply to the worker bundles. Note that [config.plugins](./shared-options#plugins) only applies to workers in dev, it should be configured here instead for build.
The function should return new plugin instances as they are used in parallel rollup worker builds. As such, modifying `config.worker` options in the `config` hook will be ignored.

## worker.rolldownOptions

* **Type:** [`RolldownOptions`](https://rolldown.rs/reference/)

Rollup options to build worker bundle.

## worker.rollupOptions

* **Type:** `RolldownOptions`
* **Deprecated**

This option is an alias of `worker.rolldownOptions` option. Use `worker.rolldownOptions` option instead.