Improve Build Performance

Rsbuild optimizes build performance by default, but as the project becomes larger, you may encounter some build performance problems.

This document provides some optional speed-up methods, developers can choose some of them to improve the build performance.

Performance Profiling

Performing a performance analysis can help you identify performance bottlenecks in your project, allowing for targeted optimization.

Please refer to the Performance Building Analysis section for more information.

General Optimization

The following are some general optimization methods, which can speed up the development build and production build.

Use Lightning CSS

Lightning CSS is a high performance CSS parser, transformer and minifier written in Rust. It supports parsing and transforming many modern CSS features into syntax supported by target browsers, and also provides a better compression ratio.

Rsbuild provides the Lightning CSS Plugin which allows you to use lightningcss instead of the built-in `postcss-loader' to compile CSS, reducing the performance overhead of PostCSS and autoprefixer.

For projects with a large number of CSS files, enabling the Lightning CSS plugin can significantly improve overall build performance.

import { pluginLightningcss } from '@rsbuild/plugin-lightningcss';

export default {
  plugins: [pluginLightningcss()],

Reducing Modules

Optimizing the number of modules referenced by the application can reduce the bundle size and improve build performance. Please read the Bundle Size Optimization section to learn some optimization methods.

Development optimization

The following are methods for improving development build performance.

Enable Lazy Compilation

Enabling lazy compilation can significantly reduce the number of modules compiled at dev startup and improve startup time.

export default {
  dev: {
    lazyCompilation: true,

Please refer to dev.lazyCompilation for more information.

Source Map Format

In order to provide a good debugging experience, Rsbuild uses the cheap-module-source-map format source map by default during development, which is a high-quality source map format and will bring certain performance overhead.

You can improve build speed by adjusting the source map format during development through output.sourceMap.

For example to disable source map:

export default {
  output: {
    sourceMap: {
      js: false,

Or set the source map format of the development environment to the cheapest eval format:

export default {
  output: {
    sourceMap: {
      js: process.env.NODE_ENV === 'development' ? 'eval' : false,

For detailed differences between different source map formats, see Rspack - devtool.

Browserslist for development

This strategy is similar to "Adjust Browserslist", the difference is that we can set different browserslist for development and production environment, thereby reducing the compilation overhead during development.

For example, you can add the following config to .browserslistrc, which means that only the latest browsers are compatible during development, and the actual browsers are compatible in the production environment:

chrome >= 87
edge >= 88
firefox >= 78
safari >= 14

last 1 chrome version
last 1 firefox version
last 1 safari version

Note that this strategy can lead to some differences in the build result of development production environment.