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

yarn add -D css-minimizer-webpack-plugin

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: {},
      }),
    ],
  },
};