mini-css-extract-plugin

What is mini-css-extract-plugin?

The mini-css-extract-plugin is a plugin for webpack that extracts CSS into separate files. It creates a CSS file per JS file which contains CSS. It supports on-demand-loading of CSS and SourceMaps. It requires webpack 4 to function.

What are mini-css-extract-plugin's main functionalities?

Extract CSS into separate files

This feature allows you to extract CSS from your bundle into a separate file, which can be loaded independently.

const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          MiniCssExtractPlugin.loader,
          'css-loader'
        ]
      }
    ]
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: '[name].css',
      chunkFilename: '[id].css'
    })
  ]
};

Lazy loading of CSS files

This feature enables on-demand loading of CSS by splitting the CSS into chunks and loading them when needed.

import(/* webpackChunkName: 'style' */ './style.css').then(() => {
  // Use style.css
});

SourceMap support

This feature allows you to generate source maps for the CSS files, which is helpful for debugging purposes.

const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader,
            options: {
              sourceMap: true
            }
          },
          {
            loader: 'css-loader',
            options: {
              sourceMap: true
            }
          }
        ]
      }
    ]
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: '[name].css',
      chunkFilename: '[id].css'
    })
  ]
};

Other packages similar to mini-css-extract-plugin

extract-text-webpack-plugin

This package is similar to mini-css-extract-plugin but was used for webpack 3 and earlier. It is now deprecated in favor of mini-css-extract-plugin, which is designed for webpack 4 and later.

style-loader

This package injects CSS into the DOM using multiple <style> tags. It is often used in development environments for hot module replacement but does not extract CSS into separate files.

sass-loader

While sass-loader itself does not extract CSS, it is commonly used in conjunction with mini-css-extract-plugin to compile Sass/SCSS files into CSS and then extract it into separate files.

README

mini-css-extract-plugin

This plugin extracts CSS into separate files. It creates a CSS file per JS file which contains CSS. It supports On-Demand-Loading of CSS and SourceMaps.

It builds on top of a new webpack v4 feature (module types) and requires webpack 4 to work.

Compared to the extract-text-webpack-plugin:

• Async loading
• No duplicate compilation (performance)
• Easier to use
• Specific to CSS

TODO:

• HMR support

Install

npm install --save-dev mini-css-extract-plugin

Usage

Configuration

Minimal example

webpack.config.js

const MiniCssExtractPlugin = require("mini-css-extract-plugin");
module.exports = {
  plugins: [
    new MiniCssExtractPlugin({
      // Options similar to the same options in webpackOptions.output
      // both options are optional
      filename: "[name].css",
      chunkFilename: "[id].css"
    })
  ],
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader,
            options: {
              // you can specify a publicPath here
              // by default it use publicPath in webpackOptions.output
              publicPath: '../'
            }
          },
          "css-loader"
        ]
      }
    ]
  }
}

Advanced configuration example

This plugin should be used only on production builds without style-loader in the loaders chain, especially if you want to have HMR in development.

Here is an example to have both HMR in development and your styles extracted in a file for production builds.

(Loaders options left out for clarity, adapt accordingly to your needs.)

webpack.config.js

const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const devMode = process.env.NODE_ENV !== 'production'

module.exports = {
  plugins: [
    new MiniCssExtractPlugin({
      // Options similar to the same options in webpackOptions.output
      // both options are optional
      filename: devMode ? '[name].css' : '[name].[hash].css',
      chunkFilename: devMode ? '[id].css' : '[id].[hash].css',
    })
  ],
  module: {
    rules: [
      {
        test: /\.(sa|sc|c)ss$/,
        use: [
          devMode ? 'style-loader' : MiniCssExtractPlugin.loader,
          'css-loader',
          'postcss-loader',
          'sass-loader',
        ],
      }
    ]
  }
}

Minimizing For Production

While webpack 5 is likely to come with a CSS minimizer built-in, with webpack 4 you need to bring your own. To minify the output, use a plugin like optimize-css-assets-webpack-plugin. Setting optimization.minimizer overrides the defaults provided by webpack, so make sure to also specify a JS minimizer:

webpack.config.js

const UglifyJsPlugin = require("uglifyjs-webpack-plugin");
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const OptimizeCSSAssetsPlugin = require("optimize-css-assets-webpack-plugin");
module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        cache: true,
        parallel: true,
        sourceMap: true // set to true if you want JS source maps
      }),
      new OptimizeCSSAssetsPlugin({})
    ]
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: "[name].css",
      chunkFilename: "[id].css"
    })
  ],
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          MiniCssExtractPlugin.loader,
          "css-loader"
        ]
      }
    ]
  }
}

Features

Using preloaded or inlined CSS

The runtime code detects already added CSS via <link> or <style> tag. This can be useful when injecting CSS on server-side for Server-Side-Rendering. The href of the <link> tag has to match the URL that will be used for loading the CSS chunk. The data-href attribute can be used for <link> and <style> too. When inlining CSS data-href must be used.

Extracting all CSS in a single file

Similar to what extract-text-webpack-plugin does, the CSS can be extracted in one CSS file using optimization.splitChunks.cacheGroups.

webpack.config.js

const MiniCssExtractPlugin = require("mini-css-extract-plugin");
module.exports = {
  optimization: {
    splitChunks: {
      cacheGroups: {
        styles: {
          name: 'styles',
          test: /\.css$/,
          chunks: 'all',
          enforce: true
        }
      }
    }
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: "[name].css",
    })
  ],
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          MiniCssExtractPlugin.loader,
          "css-loader"
        ]
      }
    ]
  }
}

Extracting CSS based on entry

You may also extract the CSS based on the webpack entry name. This is especially useful if you import routes dynamically but want to keep your CSS bundled according to entry. This also prevents the CSS duplication issue one had with the ExtractTextPlugin.

const path = require('path');
const MiniCssExtractPlugin = require("mini-css-extract-plugin");

function recursiveIssuer(m) {
  if (m.issuer) {
    return recursiveIssuer(m.issuer);
  } else if (m.name) {
    return m.name;
  } else {
    return false;
  }
}

module.exports = {
  entry: {
    foo: path.resolve(__dirname, 'src/foo'),
    bar: path.resolve(__dirname, 'src/bar')
  },
  optimization: {
    splitChunks: {
      cacheGroups: {
        fooStyles: {
          name: 'foo',
          test: (m,c,entry = 'foo') => m.constructor.name === 'CssModule' && recursiveIssuer(m) === entry,
          chunks: 'all',
          enforce: true
        },
        barStyles: {
          name: 'bar',
          test: (m,c,entry = 'bar') => m.constructor.name === 'CssModule' && recursiveIssuer(m) === entry,
          chunks: 'all',
          enforce: true
        }
      }
    }
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: "[name].css",
    })
  ],
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          MiniCssExtractPlugin.loader,
          "css-loader"
        ]
      }
    ]
  }
}

Long Term Caching

For long term caching use filename: "[contenthash].css". Optionally add [name].

Maintainers

Tobias Koppers

License

MIT

Changelog

0.4.2 (2018-08-21)

Bug Fixes

• use correct order when multiple chunk groups are merged (#246) (c3b363d)

<a name="0.4.1"></a>