css-minimizer-webpack-plugin

What is css-minimizer-webpack-plugin?

The css-minimizer-webpack-plugin is a plugin for webpack that optimizes and minimizes CSS assets. It uses cssnano to optimize CSS by removing comments, whitespace, and other unnecessary characters without affecting the functionality of the CSS code. It can be used in production builds to reduce the size of CSS files, which can lead to faster load times for web applications.

What are css-minimizer-webpack-plugin's main functionalities?

Minification of CSS

This feature allows you to integrate CSS minification into your webpack build process. By adding the CssMinimizerPlugin to the optimization.minimizer array in your webpack configuration, you can ensure that your CSS files are automatically minimized during the build.

{"optimization": {"minimizer": [new CssMinimizerPlugin()]}}

Source Map Generation

This feature enables the generation of source maps for the minimized CSS files. Source maps allow you to trace back the minified CSS to the original source files, which is useful for debugging purposes.

{"optimization": {"minimizer": [new CssMinimizerPlugin({sourceMap: true})]}}

Custom Minification Options

This feature allows you to provide custom options to the cssProcessor used by the plugin. In this example, the cssProcessorOptions are set to use the 'default' preset and configure it to remove all comments from the CSS.

{"optimization": {"minimizer": [new CssMinimizerPlugin({cssProcessorOptions: {preset: ['default', {discardComments: {removeAll: true}}]}})]}}

Other packages similar to css-minimizer-webpack-plugin

uglifyjs-webpack-plugin

The uglifyjs-webpack-plugin is a plugin for webpack that minimizes JavaScript files. While it does not handle CSS, it serves a similar purpose for JavaScript assets. It uses UglifyJS to compress and optimize JavaScript code.

terser-webpack-plugin

The terser-webpack-plugin is another webpack plugin for minimizing JavaScript files. It is similar to uglifyjs-webpack-plugin but uses Terser for minification, which supports ES6+ syntax. It is often used as a more modern alternative to uglifyjs-webpack-plugin.

optimize-css-assets-webpack-plugin

The optimize-css-assets-webpack-plugin is a plugin that can be used to optimize and minimize CSS assets. It is similar to css-minimizer-webpack-plugin but uses cssnano and can also work with other CSS processors. It is an alternative for CSS optimization in webpack builds.

README

css-minimizer-webpack-plugin

This plugin uses cssnano to optimize and minify your CSS.

Just like optimize-css-assets-webpack-plugin but more accurate with source maps and assets using query string, allows caching and works in parallel mode.

Getting Started

To begin, you'll need to install css-minimizer-webpack-plugin:

npm install css-minimizer-webpack-plugin --save-dev

or

yarn add -D css-minimizer-webpack-plugin

or

pnpm add -D css-minimizer-webpack-plugin

Then add the plugin to your webpack configuration. For example:

webpack.config.js

const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const CssMinimizerPlugin = require("css-minimizer-webpack-plugin");

module.exports = {
  module: {
    rules: [
      {
        test: /.s?css$/,
        use: [MiniCssExtractPlugin.loader, "css-loader", "sass-loader"],
      },
    ],
  },
  optimization: {
    minimizer: [
      // For webpack@5 you can use the `...` syntax to extend existing minimizers (i.e. `terser-webpack-plugin`), uncomment the next line
      // `...`,
      new CssMinimizerPlugin(),
    ],
  },
  plugins: [new MiniCssExtractPlugin()],
};

This will enable CSS optimization only in production mode.

If you want to run it also in development set the optimization.minimize option to true:

webpack.config.js

// [...]
module.exports = {
  optimization: {
    // [...]
    minimize: true,
  },
};

And run webpack via your preferred method.

Note about source maps

Works only with source-map, inline-source-map, hidden-source-map and nosources-source-map values for the devtool option.

Why? Because CSS support only these source map types.

The plugin respect the devtool and using the SourceMapDevToolPlugin plugin. Using supported devtool values enable source map generation. Using SourceMapDevToolPlugin with enabled the columns option enables source map generation.

Use source maps to map error message locations to modules (this slows down the compilation). If you use your own minify function please read the minify section for handling source maps correctly.

Options

Name	Type	Default	Description
test	String|RegExp|Array<String|RegExp>	/\.css(\?.*)?$/i	Test to match files against.
include	String|RegExp|Array<String|RegExp>	undefined	Files to include.
exclude	String|RegExp|Array<String|RegExp>	undefined	Files to exclude.
parallel	Boolean|Number	true	Enable/disable multi-process parallel running.
minify	Function|Array<Function>	CssMinimizerPlugin.cssnanoMinify	Allows to override default minify function.
minimizerOptions	Object|Array<Object>	{ preset: 'default' }	Cssnano optimisations options.
warningsFilter	Function<(warning, file, source) -> Boolean>	() => true	Allow to filter css-minimizer warnings.

test

Type: String|RegExp|Array<String|RegExp> - default: /\.css(\?.*)?$/i

Test to match files against.

module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        test: /\.foo\.css$/i,
      }),
    ],
  },
};

include

Type: String|RegExp|Array<String|RegExp> Default: undefined

Files to include.

webpack.config.js

module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        include: /\/includes/,
      }),
    ],
  },
};

exclude

Type: String|RegExp|Array<String|RegExp> Default: undefined

Files to exclude.

webpack.config.js

module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        exclude: /\/excludes/,
      }),
    ],
  },
};

parallel

Type: Boolean|Number Default: true

Use multi-process parallel running to improve the build speed. Default number of concurrent runs: os.cpus().length - 1.

ℹ️ Parallelization can speed up your build significantly and is therefore highly recommended. If a parallelization is enabled, the packages in minimizerOptions must be required via strings (packageName or require.resolve(packageName)). Read more in minimizerOptions

Boolean

Enable/disable multi-process parallel running.

webpack.config.js

module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        parallel: true,
      }),
    ],
  },
};

Number

Enable multi-process parallel running and set number of concurrent runs.

webpack.config.js

module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        parallel: 4,
      }),
    ],
  },
};

minify

Type: Function|Array<Function> Default: CssMinimizerPlugin.cssnanoMinify

Allows overriding default minify function. By default, plugin uses cssnano package. Useful for using and testing unpublished versions or forks.

Possible options:

• CssMinimizerPlugin.cssnanoMinify
• CssMinimizerPlugin.cssoMinify
• CssMinimizerPlugin.cleanCssMinify
• CssMinimizerPlugin.esbuildMinify
• CssMinimizerPlugin.lightningCssMinify (previouslyCssMinimizerPlugin.parcelCssMinify, the package was renamed, but we keep it for backward compatibility)
• async (data, inputMap, minimizerOptions) => {return {code: "a{color: red}", map: "...", warnings: [], errors: []}}

Warning

Always use require inside minify function when parallel option enabled.

Function

webpack.config.js

module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minimizerOptions: {
          level: {
            1: {
              roundingPrecision: "all=3,px=5",
            },
          },
        },
        minify: CssMinimizerPlugin.cleanCssMinify,
      }),
    ],
  },
};

Array

If an array of functions is passed to the minify option, the minimizerOptions must also be an array. The function index in the minify array corresponds to the options object with the same index in the minimizerOptions array.

webpack.config.js

module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minimizerOptions: [
          {}, // Options for the first function (CssMinimizerPlugin.cssnanoMinify)
          {}, // Options for the second function (CssMinimizerPlugin.cleanCssMinify)
          {}, // Options for the third function
        ],
        minify: [
          CssMinimizerPlugin.cssnanoMinify,
          CssMinimizerPlugin.cleanCssMinify,
          async (data, inputMap, minimizerOptions) => {
            // To do something
            return {
              code: `a{color: red}`,
              map: `{"version": "3", ...}`,
              warnings: [],
              errors: [],
            };
          },
        ],
      }),
    ],
  },
};

minimizerOptions

Type: Object|Array<Object> Default: { preset: 'default' }

Cssnano optimisations options.

Object

module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minimizerOptions: {
          preset: [
            "default",
            {
              discardComments: { removeAll: true },
            },
          ],
        },
      }),
    ],
  },
};

Array

The function index in the minify array corresponds to the options object with the same index in the minimizerOptions array. If you use minimizerOptions like object, all minify function accept it.

If a parallelization is enabled, the packages in minimizerOptions must be required via strings (packageName or require.resolve(packageName)). In this case, we shouldn't use require/import.

module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minimizerOptions: {
          preset: require.resolve("cssnano-preset-simple"),
        },
      }),
    ],
  },
};

processorOptions (⚠ only cssnano)

Type: Object Default: { from: assetName }

Allows filtering options processoptions for the cssnano. The parser, stringifier and syntax can be either a function or a string indicating the module that will be imported.

Warning

If a function is passed, the parallel option must be disabled..

import sugarss from "sugarss";

module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        parallel: false,
        minimizerOptions: {
          processorOptions: {
            parser: sugarss,
          },
        },
      }),
    ],
  },
};

module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minimizerOptions: {
          processorOptions: {
            parser: "sugarss",
          },
        },
      }),
    ],
  },
};

warningsFilter

Type: Function<(warning, file, source) -> Boolean> Default: () => true

Allow filtering css-minimizer warnings (By default cssnano). Return true to keep the warning, a falsy value (false/null/undefined) otherwise.

Warning

The source argument will contain undefined if you don't use source maps.

webpack.config.js

module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        warningsFilter: (warning, file, source) => {
          if (/Dropping unreachable code/i.test(warning)) {
            return true;
          }

          if (/file\.css/i.test(file)) {
            return true;
          }

          if (/source\.css/i.test(source)) {
            return true;
          }

          return false;
        },
      }),
    ],
  },
};

Examples

Use sourcemaps

Don't forget to enable sourceMap options for all loaders.

const CssMinimizerPlugin = require("css-minimizer-webpack-plugin");

module.exports = {
  devtool: "source-map",
  module: {
    rules: [
      {
        test: /.s?css$/,
        use: [
          MiniCssExtractPlugin.loader,
          { loader: "css-loader", options: { sourceMap: true } },
          { loader: "sass-loader", options: { sourceMap: true } },
        ],
      },
    ],
  },
  optimization: {
    minimizer: [new CssMinimizerPlugin()],
  },
  plugins: [new MiniCssExtractPlugin()],
};

Remove all comments

Remove all comments (including comments starting with /*!).

module.exports = {
  optimization: {
    minimizer: [
      new CssMinimizerPlugin({
        minimizerOptions: {
          preset: [
            "default",
            {
              discardComments: { removeAll: true },
            },
          ],
        },
      }),
    ],
  },
};

Using custom minifier csso

webpack.config.js

module.exports = {
  // Uncomment if you need source maps
  // devtool: "source-map",
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minify: CssMinimizerPlugin.cssoMinify,
        // Uncomment this line for options
        // minimizerOptions: { restructure: false },
      }),
    ],
  },
};

Using custom minifier clean-css

webpack.config.js

module.exports = {
  // Uncomment if you need source maps
  // devtool: "source-map",
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minify: CssMinimizerPlugin.cleanCssMinify,
        // Uncomment this line for options
        // minimizerOptions: { compatibility: 'ie11,-properties.merging' },
      }),
    ],
  },
};

Using custom minifier esbuild

webpack.config.js

module.exports = {
  // Uncomment if you need source maps
  // devtool: "source-map",
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minify: CssMinimizerPlugin.esbuildMinify,
      }),
    ],
  },
};

Using custom minifier lightningcss, previously @parcel/css

webpack.config.js

module.exports = {
  // Uncomment if you need source maps
  // devtool: "source-map",
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minify: CssMinimizerPlugin.lightningCssMinify,
        // Uncomment this line for options
        // minimizerOptions: { targets: { ie: 11 }, drafts: { nesting: true } },
      }),
    ],
  },
};

Using custom minifier swc

webpack.config.js

module.exports = {
  // Uncomment if you need source maps
  // devtool: "source-map",
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        minify: CssMinimizerPlugin.swcMinify,
        // Uncomment this line for options
        // minimizerOptions: {},
      }),
    ],
  },
};

Contributing

Please take a moment to read our contributing guidelines if you haven't yet done so.

CONTRIBUTING

License

MIT

Changelog

5.0.0 (2023-03-27)

⚠ BREAKING CHANGES

• update cssnano to v6 (migration guide - https://github.com/cssnano/cssnano/releases/tag/cssnano%406.0.0) (#224)

Features

• update cssnano to v6 (#224) (cfcae0c)