#Improve build performance

While Rsbuild optimizes build performance by default, performance issues can arise as your project grows.

This document provides optional optimization strategies to improve build performance.

#Performance profiling

Performance profiling helps identify bottlenecks in your project for targeted optimization.

See the Build Performance Analysis section.

#General optimization

These general optimization methods speed up both development and production builds.

#Upgrade Rsbuild

Upgrading to the latest version of Rsbuild gives you access to the latest performance optimizations. See Upgrade Rsbuild for more details.

#Enable persistent cache

Rsbuild provides a performance.buildCache configuration that significantly improves rebuild speed.

#React Compiler

If your project uses React Compiler, enable Rsbuild's built-in Rust version of React Compiler instead of running React Compiler through Babel to reduce the performance overhead introduced by Babel.

#Reduce module count

Optimizing the number of modules in your application reduces bundle size and improves build performance. See Bundle Size Optimization to learn optimization strategies.

#Parallel processing

Some plugins support processing modules in parallel using worker threads. When enabled, modules are processed across multiple worker threads, reducing pressure on the main thread and improving overall build performance when compiling large numbers of modules.

The following plugins support the parallel option:

• @rsbuild/plugin-babel - parallel: run Babel transformations in parallel.
• @rsbuild/plugin-less - parallel: compile Less modules in parallel.
• @rsbuild/plugin-svgr - parallel: transform SVG modules into React components in parallel.

#Tool selection

While Rsbuild delivers excellent build performance out of the box, certain JavaScript-based tools can negatively impact performance, particularly in large projects.

• @rsbuild/plugin-babel: This plugin uses Babel. We recommend using the more performant SWC for code transformation instead.
• @rsbuild/plugin-less: The Less compiler has relatively poor performance. Consider using @rsbuild/plugin-sass or other performant CSS solutions instead.
• @rsbuild/plugin-type-check: The default TypeScript-based type-checking approach has relatively poor performance. We recommend enabling experimental typescript-go support to improve type-checking performance.
• terser-webpack-plugin or minimizer-webpack-plugin: You can replace Terser with faster minimizers like Rsbuild's built-in SWC minifier.

#Optimize Tailwind CSS

When using Tailwind CSS v3, incorrectly configuring the content field in tailwind.config.js can lead to poor build and HMR performance.

See Tailwind CSS v3 - Optimize build performance for more details.

#Development optimization

These methods improve performance in development mode.

#Enable lazy compilation

Enabling lazy compilation significantly reduces the number of modules compiled during dev server startup, improving startup time.

export default {
  dev: {
    lazyCompilation: true,
  },
};

See dev.lazyCompilation for more information.

#Enable native watcher

Enabling Rspack's native watcher improves HMR performance in development mode.

export default {
  tools: {
    rspack: {
      experiments: {
        nativeWatcher: true,
      },
    },
  },
};

#Source map format

To provide a good debugging experience, Rsbuild uses the cheap-module-source-map format in development mode by default. This is a high-quality source map format that comes with some performance overhead.

You can improve build speed by adjusting the source map format using output.sourceMap.

For example, to disable source maps:

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

Or set the source map format to the fastest eval format in development mode:

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", except you can set different browserslist configurations for development and production, reducing compilation overhead in development.

For example, you can add the following config to .browserslistrc to target only the latest browsers in development while supporting a broader range in production:

[production]
chrome >= 107
edge >= 107
firefox >= 104
safari >= 16

[development]
last 1 chrome version
last 1 firefox version
last 1 safari version

Note that this can lead to differences in build output between development and production modes.