---
title: Parallel Build Without Build Worker
---

## Why This Error Occurred

The `experimental.parallelServerCompiles` and `experimental.parallelServerBuildTraces`
options require that the `experimental.webpackBuildWorker` option is set to `true`. These
options use workers to improve the parallelization of the build which may improve performance,
but the build may use more memory at the same time.

## Possible Ways to Fix It

Build workers are enabled by default unless you have a custom webpack config. You can force enable the option by setting `experimental.webpackBuildWorker: true` in your `next.config.js` file, but some webpack configuration options may not be compatible.

## Useful Links

- [Webpack Build Worker automatic opt-out](/docs/messages/webpack-build-worker-opt-out)