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

Plugin Options

Name	Type	Default	Description
filename	{String|Function}	[name].css	This option determines the name of each output CSS file
chunkFilename	{String|Function}	based on filename	This option determines the name of non-entry chunk files
ignoreOrder	{Boolean}	false	Remove Order Warnings
insert	{String|Function}	document.head.appendChild(linkTag);	Inserts <link> at the given position
attributes	{Object}	{}	Adds custom attributes to tag
linkType	{String|Boolean}	text/css	Allows loading asynchronous chunks with a custom link type

filename

Type: String|Function Default: [name].css

This option determines the name of each output CSS file.

Works like output.filename

chunkFilename

Type: String|Function Default: based on filename

i Specifying chunkFilename as a function is only available in webpack@5

This option determines the name of non-entry chunk files.

Works like output.chunkFilename

ignoreOrder

Type: Boolean Default: false

Remove Order Warnings. See examples below for details.

insert

Type: String|Function Default: document.head.appendChild(linkTag);

By default, the extract-css-chunks-plugin appends styles (<link> elements) to document.head of the current window.

However in some circumstances it might be necessary to have finer control over the append target or even delay link elements instertion. For example this is the case when you asynchronously load styles for an application that runs inside of an iframe. In such cases insert can be configured to be a function or a custom selector.

If you target an iframe make sure that the parent document has sufficient access rights to reach into the frame document and append elements to it.

String

Allows to setup custom query selector. A new <link> element will be inserted after the found item.

webpack.config.js

new MiniCssExtractPlugin({
  insert: '#some-element',
});

A new <link> element will be inserted after the element with id some-element.

Function

Allows to override default behavior and insert styles at any position.

⚠ Do not forget that this code will run in the browser alongside your application. Since not all browsers support latest ECMA features like let, const, arrow function expression and etc we recommend you to use only ECMA 5 features and syntax.

⚠ The insert function is serialized to string and passed to the plugin. This means that it won't have access to the scope of the webpack configuration module.

webpack.config.js

new MiniCssExtractPlugin({
  insert: function (linkTag) {
    var reference = document.querySelector('#some-element');
    if (reference) {
      reference.parentNode.insertBefore(linkTag, reference);
    }
  },
});

A new <link> element will be inserted before the element with id some-element.

attributes

Type: Object Default: {}

If defined, the mini-css-extract-plugin will attach given attributes with their values on element.

webpack.config.js

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

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

Note: It's only applied to dynamically loaded css chunks, if you want to modify link attributes inside html file, please using html-webpack-plugin

linkType

Type: String|Boolean Default: text/css

This option allows loading asynchronous chunks with a custom link type, such as <link type="text/css" ...>.

String

Possible values: text/css

webpack.config.js

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

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

Boolean

false disables the link type attribute

webpack.config.js

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

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

Loader Options

Name	Type	Default	Description
publicPath	{String|Function}	webpackOptions.output.publicPath	Specifies a custom public path for the external resources like images, files, etc
esModule	{Boolean}	true	Use ES modules syntax
modules	{Object}	undefined	Configuration CSS Modules

publicPath

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

Specifies a custom public path for the external resources like images, files, etc inside CSS. Works like output.publicPath

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: true

By default, mini-css-extract-plugin generates JS modules that use the ES 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 CommonJS 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: false,
            },
          },
          '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: '../',
            },
          },
          'css-loader',
        ],
      },
    ],
  },
};

Common use case

mini-css-extract-plugin is more often used in production mode to get separate css files. For development mode (including webpack-dev-server) you can use style-loader, because it injects CSS into the DOM using multiple and works faster.

i Do not use together style-loader and mini-css-extract-plugin.

webpack.config.js

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

const plugins = [];
if (!devMode) {
  // enable in production only
  plugins.push(new MiniCssExtractPlugin());
}

module.exports = {
  plugins,
  module: {
    rules: [
      {
        test: /\.(sa|sc|c)ss$/,
        use: [
          devMode ? 'style-loader' : MiniCssExtractPlugin.loader,
          'css-loader',
          'postcss-loader',
          'sass-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 not be used with style-loader in the loaders chain.

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.)

You should not use HotModuleReplacementPlugin plugin if you are using a webpack-dev-server. webpack-dev-server enables / disables HMR using hot option.

webpack.config.js

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

const plugins = [
  new MiniCssExtractPlugin({
    // Options similar to the same options in webpackOptions.output
    // both options are optional
    filename: devMode ? '[name].css' : '[name].[contenthash].css',
    chunkFilename: devMode ? '[id].css' : '[id].[contenthash].css',
  }),
];
if (devMode) {
  // only enable hot in development
  plugins.push(new webpack.HotModuleReplacementPlugin());
}

module.exports = {
  plugins,
  module: {
    rules: [
      {
        test: /\.(sa|sc|c)ss$/,
        use: [
          MiniCssExtractPlugin.loader,
          'css-loader',
          'postcss-loader',
          'sass-loader',
        ],
      },
    ],
  },
};

Hot Module Reloading (HMR)

Note: HMR is automatically supported in webpack 5. No need to configure it. Skip the following:

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.

You should not use HotModuleReplacementPlugin plugin if you are using a webpack-dev-server. webpack-dev-server enables / disables HMR using hot option.

webpack.config.js

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

const plugins = [
  new MiniCssExtractPlugin({
    // Options similar to the same options in webpackOptions.output
    // both options are optional
    filename: devMode ? '[name].css' : '[name].[contenthash].css',
    chunkFilename: devMode ? '[id].css' : '[id].[contenthash].css',
  }),
];
if (devMode) {
  // only enable hot in development
  plugins.push(new webpack.HotModuleReplacementPlugin());
}

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

Minimizing For Production

To minify the output, use a plugin like css-minimizer-webpack-plugin.

webpack.config.js

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

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

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.

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, c) {
  const issuer = c.moduleGraph.getIssuer(m);
  // For webpack@4 chunks = m.issuer

  if (issuer) {
    return recursiveIssuer(issuer, c);
  }

  const chunks = c.chunkGraph.getModuleChunks(m);
  // For webpack@4 chunks = m._chunks

  for (const chunk of chunks) {
    return chunk.name;
  }

  return false;
}

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

Filename Option as function

With the filename 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 filename to output the generated css into a different directory.

webpack.config.js

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

module.exports = {
  plugins: [
    new MiniCssExtractPlugin({
      filename: ({ chunk }) => `${chunk.name.replace('/js/', '/css/')}.css`,
    }),
  ],
  module: {
    rules: [
      {
        test: /\.css$/,
        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

Changelog

1.2.1 (2020-10-27)

Bug Fixes

• onerror/onload memory leak (#640) (2b6fcf2)