CssMinimizerWebpackPlugin

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 to cache 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

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

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.

And run webpack via your preferred method.

Options

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/,
      }),
    ],
  },
};

cache

⚠ Ignored in webpack 5! Please use https://webpack.js.org/configuration/other-options/#cache.

Type: Boolean|String Default: true

Enable file caching. Default path to cache directory: node_modules/.cache/css-minimizer-webpack-plugin.

ℹ️ If you use your own minify function please read the minify section for cache invalidation correctly.

Boolean

Enable/disable file caching.

webpack.config.js

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

String

Enable file caching and set path to cache directory.

webpack.config.js

module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        cache: 'path/to/cache',
      }),
    ],
  },
};

cacheKeys

⚠ Ignored in webpack 5! Please use https://webpack.js.org/configuration/other-options/#cache.

Type: Function<(defaultCacheKeys, file) -> Object> Default: defaultCacheKeys => defaultCacheKeys

Allows you to override default cache keys.

Default cache keys:

({
  cssMinimizer: require('cssnano/package.json').version, // cssnano version
  'css-minimizer-webpack-plugin': require('../package.json').version, // plugin version
  'css-minimizer-webpack-plugin-options': this.options, // plugin options
  path: compiler.outputPath ? `${compiler.outputPath}/${file}` : file, // asset path
  hash: crypto.createHash('md4').update(input).digest('hex'), // source file hash
});

webpack.config.js

module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        cache: true,
        cacheKeys: (defaultCacheKeys, file) => {
          defaultCacheKeys.myCacheKey = 'myCacheKeyValue';

          return defaultCacheKeys;
        },
      }),
    ],
  },
};

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 speedup your build significantly and is therefore highly recommended.

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,
      }),
    ],
  },
};

sourceMap

Type: Boolean|Object Default: false (see below for details around devtool value and SourceMapDevToolPlugin plugin)

Enable (and configure) source map support. Use PostCss SourceMap options. Default configuration when enabled: { inline: false }.

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.

webpack.config.js

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

minify

Type: Function Default: undefined

Allows you to override default minify function. By default plugin uses cssnano package. Useful for using and testing unpublished versions or forks.

⚠️ Always use require inside minify function when parallel option enabled.

webpack.config.js

module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        sourceMap: true,
        minify: (data, inputMap, minimizerOptions) => {
          const postcss = require('postcss');

          const plugin = postcss.plugin(
            'custom-plugin',
            () => (css, result) => {
              // custom code
            }
          );

          const [[filename, input]] = Object.entries(data);

          const postcssOptions = {
            from: filename,
            to: filename,
            map: {
              prev: inputMap,
            },
          };

          return postcss([plugin])
            .process(input, postcssOptions)
            .then((result) => {
              return {
                css: result.css,
                map: result.map,
                warnings: result.warnings(),
              };
            });
        },
      }),
    ],
  },
};

minimizerOptions

Type: Object Default: { preset: 'default' }

Cssnano optimisations options.

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

warningsFilter

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

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

⚠️ 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 = {
  module: {
    loaders: [
      {
        test: /.s?css$/,
        use: [
          MiniCssExtractPlugin.loader,
          { loader: 'css-loader', options: { sourceMap: true } },
          { loader: 'sass-loader', options: { sourceMap: true } },
        ],
      },
    ],
  },
  optimization: {
    minimizer: [
      new CssMinimizerPlugin({
        sourceMap: true,
      }),
    ],
  },
};

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

By default plugin uses cssnano package. It is possible to use another minify function.

⚠️ Always use require inside minify function when parallel option enabled.

webpack.config.js

module.exports = {
  devtool: 'source-map',
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        sourceMap: true,
        minify: async (data, inputMap) => {
          const csso = require('csso');
          const sourcemap = require('source-map');

          const [[filename, input]] = Object.entries(data);
          const minifiedCss = csso.minify(input, {
            filename: filename,
            sourceMap: true,
          });

          if (inputMap) {
            minifiedCss.map.applySourceMap(
              new sourcemap.SourceMapConsumer(inputMap),
              filename
            );
          }

          return {
            css: minifiedCss.css,
            map: minifiedCss.map.toJSON(),
          };
        },
      }),
    ],
  },
};

Using custom minifier clean-css

By default plugin uses cssnano package. It is possible to use another minify function.

⚠️ Always use require inside minify function when parallel option enabled.

webpack.config.js

module.exports = {
  devtool: 'source-map',
  optimization: {
    minimize: true,
    minimizer: [
      new CssMinimizerPlugin({
        sourceMap: true,
        minify: async (data, inputMap) => {
          // eslint-disable-next-line global-require
          const CleanCSS = require('clean-css');

          const [[filename, input]] = Object.entries(data);
          const minifiedCss = await new CleanCSS({ sourceMap: true }).minify({
            [filename]: https://github.com/webpack-contrib/css-minimizer-webpack-plugin/blob/master/%7B
              styles: input,
              sourceMap: inputMap,
            },
          });

          return {
            css: minifiedCss.styles,
            map: minifiedCss.sourceMap.toJSON(),
            warnings: minifiedCss.warnings,
          };
        },
      }),
    ],
  },
};

Contributing

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

CONTRIBUTING

License

MIT