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

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

Getting Started

To begin, you'll need to install mini-css-extract-plugin:

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

It's recommended to combine mini-css-extract-plugin with the css-loader

Then add the loader and the plugin to your webpack config. For example:

style.css

body {
  background: green;
}

component.js

import './style.css';

webpack.config.js

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

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

Options

publicPath

Type: String|Function Default: the publicPath in webpackOptions.output

Specifies a custom public path for the target file(s).

String

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: {
              publicPath: '/public/path/to/',
            },
          },
          'css-loader',
        ],
      },
    ],
  },
};

Function

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: {
              publicPath: (resourcePath, context) => {
                return path.relative(path.dirname(resourcePath), context) + '/';
              },
            },
          },
          'css-loader',
        ],
      },
    ],
  },
};

esModule

Type: Boolean Default: false

By default, mini-css-extract-plugin generates JS modules that use the CommonJS modules syntax. There are some cases in which using ES modules is beneficial, like in the case of module concatenation and tree shaking.

You can enable a ES module syntax using:

webpack.config.js

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

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

modules

Type: Object Default: undefined

Configuration CSS Modules.

namedExport

Type: Boolean Default: false

Enables/disables ES modules named export for locals.

⚠ Names of locals are converted to camelCase.

⚠ It is not allowed to use JavaScript reserved words in css class names.

⚠ Options esModule and modules.namedExport in css-loader and MiniCssExtractPlugin.loader should be enabled.

styles.css

.foo-baz {
  color: red;
}
.bar {
  color: blue;
}

index.js

import { fooBaz, bar } from './styles.css';

console.log(fooBaz, bar);

You can enable a ES module named export using:

webpack.config.js

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

module.exports = {
  plugins: [new MiniCssExtractPlugin()],
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader,
            options: {
              esModule: true,
              modules: {
                namedExport: true,
              },
            },
          },
          {
            loader: 'css-loader',
            options: {
              esModule: true,
              modules: {
                namedExport: true,
                localIdentName: 'foo__[name]__[local]',
              },
            },
          },
        ],
      },
    ],
  },
};

Examples

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
      // all options are optional
      filename: '[name].css',
      chunkFilename: '[id].css',
      ignoreOrder: false, // Enable to remove warnings about conflicting order
    }),
  ],
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader,
            options: {
              // you can specify a publicPath here
              // by default it uses publicPath in webpackOptions.output
              publicPath: '../',
              hmr: process.env.NODE_ENV === 'development',
            },
          },
          'css-loader',
        ],
      },
    ],
  },
};

The publicPath option as function

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: {
              publicPath: (resourcePath, context) => {
                // publicPath is the relative path of the resource to the context
                // e.g. for ./css/admin/main.css the publicPath will be ../../
                // while for ./css/main.css the publicPath will be ../
                return path.relative(path.dirname(resourcePath), context) + '/';
              },
            },
          },
          '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: [
          {
            loader: MiniCssExtractPlugin.loader,
            options: {
              hmr: process.env.NODE_ENV === 'development',
            },
          },
          'css-loader',
          'postcss-loader',
          'sass-loader',
        ],
      },
    ],
  },
};

Hot Module Reloading (HMR)

The mini-css-extract-plugin supports hot reloading of actual css files in development. Some options are provided to enable HMR of both standard stylesheets and locally scoped CSS or CSS modules. Below is an example configuration of mini-css for HMR use with CSS modules.

While we attempt to hmr css-modules. It is not easy to perform when code-splitting with custom chunk names. reloadAll is an option that should only be enabled if HMR isn't working correctly. The core challenge with css-modules is that when code-split, the chunk ids can and do end up different compared to the filename.

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: {
              // only enable hot in development
              hmr: process.env.NODE_ENV === 'development',
              // if hmr does not work, this is a forceful method.
              reloadAll: true,
            },
          },
          'css-loader',
        ],
      },
    ],
  },
};

Minimizing For Production

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 TerserJSPlugin = require('terser-webpack-plugin');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const OptimizeCSSAssetsPlugin = require('optimize-css-assets-webpack-plugin');

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

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

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'],
      },
    ],
  },
};

Module Filename Option

With the moduleFilename option you can use chunk data to customize the filename. This is particularly useful when dealing with multiple entry points and wanting to get more control out of the filename for a given entry point/chunk. In the example below, we'll use moduleFilename to output the generated css into a different directory.

webpack.config.js

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

module.exports = {
  plugins: [
    new MiniCssExtractPlugin({
      moduleFilename: ({ name }) => `${name.replace('/js/', '/css/')}.css`,
    }),
  ],
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [MiniCssExtractPlugin.loader, 'css-loader'],
      },
    ],
  },
};

Long Term Caching

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

webpack.config.js

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

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

Remove Order Warnings

For projects where css ordering has been mitigated through consistent use of scoping or naming conventions, the css order warnings can be disabled by setting the ignoreOrder flag to true for the plugin.

webpack.config.js

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

module.exports = {
  plugins: [
    new MiniCssExtractPlugin({
      ignoreOrder: true,
    }),
  ],
  module: {
    rules: [
      {
        test: /\.css$/i,
        use: [MiniCssExtractPlugin.loader, 'css-loader'],
      },
    ],
  },
};

Media Query Plugin

If you'd like to extract the media queries from the extracted CSS (so mobile users don't need to load desktop or tablet specific CSS anymore) you should use one of the following plugins:

• Media Query Plugin
• Media Query Splitting Plugin

Contributing

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

CONTRIBUTING

License

MIT