webpack5-module-minifier-plugin

@rushstack/webpack5-module-minifier-plugin

This package contains a plugin for webpack 5 that performs minification on a per-module basis rather than per-asset to deduplicate and parallelize compression work.

Installation

npm install @rushstack/webpack5-module-minifier-plugin --save-dev

Overview

This Webpack plugin performs minification of production assets on a per-module basis, rather than minifying an entire chunk at a time. It issues async calls to the minifier for each unique module and each unique set of chunk boilerplate (i.e. the webpack runtime and the structure of the module list). This improves minification time by:

• Avoiding duplicate work for each module that is included in multiple distinct assets/chunks (this is common with async chunks)
• Handing smaller code chunks to the minifier at a time (AST analysis is superlinear in size of the AST)
• Even single asset builds will likely still contain multiple modules in the final output, which can be split across available CPU cores

Use with [hash] and [contenthash] tokens

The plugin will do its best to update webpack hashes if changing the direct inputs (useSourceMap) to the plugin, but if altering the minifier property itself, you may need to use the output.hashSalt property to force a change to the hashes, especially if leveraging the MessagePortMinifier or similar, since it has no direct access to the configuration of the minifier.

Parallel execution

const { ModuleMinifierPlugin } = require('@rushstack/webpack5-module-minifier-plugin');
const { WorkerPoolMinifier } = require('@rushstack/module-minifier');

// In your webpack options:
optimization: {
  minimizer: [
    new ModuleMinifierPlugin({
      minifier: new WorkerPoolMinifier(),
      // If not provided, the plugin will attempt to guess from `mode` and `devtool`.
      // Providing it expressly gives better results
      useSourceMap: true
    })
  ]
}

Single-threaded execution

You can also run the ModuleMinifierPlugin in a single-threaded configuration.

// webpack.config.js
const { ModuleMinifierPlugin } = require('@rushstack/webpack5-module-minifier-plugin');
const { LocalMinifier } = require('@rushstack/module-minifier');

// In your webpack options:
optimization: {
  minimizer: [
    new ModuleMinifierPlugin({
      minifier: new LocalMinifier()
    })
  ]
}

License comments

By default, the plugin extracts license comments into a companion .LICENSE.txt asset and adds a reference banner to the JavaScript chunk.

Set inlineShortLicenses: true in the ModuleMinifierPlugin options to inline the complete license text when it is smaller than that banner. The comparison uses UTF-8 byte lengths after deduplicating all license comments in the chunk. Equal-size and larger notices remain in companion assets.

new ModuleMinifierPlugin({
  minifier: new LocalMinifier(),
  inlineShortLicenses: true
});

The decision is made before emitting the companion asset. Inlined comments participate in source-map generation, module-position metadata, and content hashes.

Links

• CHANGELOG.md - Find out what's new in the latest version

@rushstack/webpack5-module-minifier-plugin is part of the Rush Stack family of projects.