#Mode

• Type: 'production' | 'development' | 'none'

The mode configuration is used to set the build mode of Rspack to enable the default optimization strategy.

#Default value

If mode is not specified:

• When using @rspack/cli, rspack dev and rspack serve default to 'development', and rspack build defaults to 'production'.
• When using JavaScript API, the mode option defaults to 'production'.

#Usage

You can set the mode directly in Rspack config:

export default {
  mode: 'production',
};

In actual scenarios, you can dynamically set the mode according to process.env.NODE_ENV:

const isProduction = process.env.NODE_ENV === 'production';

export default {
  mode: isProduction ? 'production' : 'development',
};

Alternatively, you can set the mode using the --mode option on the Rspack CLI:

rspack --mode=production

#Optional values

mode has the following optional values:

#production

In production mode, Rspack automatically enables the following optimization strategies:

• Set the default value of optimization.nodeEnv to 'production', which replaces process.env.NODE_ENV in code with 'production'.
• Set the default value of optimization.minimize to true, and enable the default JavaScript and CSS minimizers.
• Set the default value of optimization.concatenateModules to true to enable module concatenation (scope hoisting).
• Set the default values of optimization.sideEffects, optimization.usedExports, optimization.mangleExports, and optimization.innerGraph for more aggressive tree shaking and export optimization.
• Set the default values of optimization.moduleIds and optimization.chunkIds to 'deterministic' for more stable long-term caching.
• Set the default value of optimization.realContentHash to true.

#development

In development mode, Rspack automatically enables the following optimization strategies:

• Set the default value of optimization.nodeEnv to 'development', which replaces process.env.NODE_ENV in code with 'development'.
• Set the default value of devtool to 'cheap-module-source-map' for easier debugging.
• Set the default value of cache to true to enable memory caching for faster development builds.
• Set the default values of optimization.moduleIds and optimization.chunkIds to 'named' for more readable module and chunk names.
• Set the default value of optimization.emitOnErrors to true, which keeps emitting output when build fails to support local debugging.

#none

When mode is set to 'none', Rspack will not enable any default optimization strategies.