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css-loader

The css-loader interprets @import and url() like import/require() and will resolve them.

Getting Started

To begin, you'll need to install css-loader:

npm install --save-dev css-loader

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

file.js

import css from 'file.css';

webpack.config.js

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

Good loaders for requiring your assets are the file-loader and the url-loader which you should specify in your config (see below).

And run webpack via your preferred method.

`toString`

You can also use the css-loader results directly as a string, such as in Angular's component style.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        use: ['to-string-loader', 'css-loader'],
      },
    ],
  },
};

const css = require('./test.css').toString();

console.log(css); // {String}

If there are SourceMaps, they will also be included in the result string.

If, for one reason or another, you need to extract CSS as a plain string resource (i.e. not wrapped in a JS module) you might want to check out the extract-loader. It's useful when you, for instance, need to post process the CSS as a string.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        use: [
          'handlebars-loader', // handlebars loader expects raw resource string
          'extract-loader',
          'css-loader',
        ],
      },
    ],
  },
};

Options

Name	Type	Default	Description
Name Type Default Description `url` `{Boolean\\|Function}`	`{Boolean\\|Function}`	`true`	Enables/Disables `url` / `image-set` functions handling
Name Type Default Description `import` `{Boolean\\|Function}`	`{Boolean\\|Function}`	`true`	Enables/Disables `@import` at-rules handling
Name Type Default Description `modules` `{Boolean\\|String\\|Object}`	`{Boolean\\|String\\|Object}`	`false`	Enables/Disables CSS Modules and their configuration
Name Type Default Description `sourceMap` `{Boolean}`	`{Boolean}`	`false`	Enables/Disables generation of source maps
Name Type Default Description `importLoaders` `{Number}`	`{Number}`	`0`	Enables/Disables or setups number of loaders applied before CSS loader
Name Type Default Description `localsConvention` `{String}`	`{String}`	`'asIs'`	Style of exported classnames
Name Type Default Description `onlyLocals` `{Boolean}`	`{Boolean}`	`false`	Export only locals
Name Type Default Description `esModule` `{Boolean}`	`{Boolean}`	`false`	Use ES modules syntax

`url`

Type: Boolean|Function Default: true

Enables/Disables url/image-set functions handling. Control url() resolving. Absolute URLs and root-relative URLs are not resolving.

Examples resolutions:

url(image.png) => require('./image.png')
url('image.png') => require('./image.png')
url(./image.png) => require('./image.png')
url('./image.png') => require('./image.png')
url('http://dontwritehorriblecode.com/2112.png') => require('http://dontwritehorriblecode.com/2112.png')
image-set(url('image2x.png') 1x, url('image1x.png') 2x) => require('./image1x.png') and require('./image2x.png')

To import assets from a node_modules path (include resolve.modules) and for alias, prefix it with a ~:

url(~module/image.png) => require('module/image.png')
url('~module/image.png') => require('module/image.png')
url(~aliasDirectory/image.png) => require('otherDirectory/image.png')

`Boolean`

Enable/disable url() resolving.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          url: true,
        },
      },
    ],
  },
};

`Function`

Allow to filter url(). All filtered url() will not be resolved (left in the code as they were written).

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          url: (url, resourcePath) => {
            // resourcePath - path to css file

            // Don't handle `img.png` urls
            if (url.includes('img.png')) {
              return false;
            }

            return true;
          },
        },
      },
    ],
  },
};

`import`

Type: Boolean|Function Default: true

Enables/Disables @import at-rules handling. Control @import resolving. Absolute urls in @import will be moved in runtime code.

Examples resolutions:

@import 'style.css' => require('./style.css')
@import url(style.css) => require('./style.css')
@import url('style.css') => require('./style.css')
@import './style.css' => require('./style.css')
@import url(./style.css) => require('./style.css')
@import url('./style.css') => require('./style.css')
@import url('http://dontwritehorriblecode.com/style.css') => @import url('http://dontwritehorriblecode.com/style.css') in runtime

To import styles from a node_modules path (include resolve.modules) and for alias, prefix it with a ~:

@import url(~module/style.css) => require('module/style.css')
@import url('~module/style.css') => require('module/style.css')
@import url(~aliasDirectory/style.css) => require('otherDirectory/style.css')

`Boolean`

Enable/disable @import resolving.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          import: true,
        },
      },
    ],
  },
};

`Function`

Allow to filter @import. All filtered @import will not be resolved (left in the code as they were written).

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          import: (parsedImport, resourcePath) => {
            // parsedImport.url - url of `@import`
            // parsedImport.media - media query of `@import`
            // resourcePath - path to css file

            // Don't handle `style.css` import
            if (parsedImport.url.includes('style.css')) {
              return false;
            }

            return true;
          },
        },
      },
    ],
  },
};

`modules`

Type: Boolean|String|Object Default: false

Enables/Disables CSS Modules and their configuration.

The modules option enables/disables the CSS Modules specification and setup basic behaviour.

Using false value increase performance because we avoid parsing CSS Modules features, it will be useful for developers who use vanilla css or use other technologies.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          modules: true,
        },
      },
    ],
  },
};

`Features`

`Scope`

Using local value requires you to specify :global classes. Using global value requires you to specify :local classes. Using pure value requires selectors must contain at least one local class or id.

You can find more information here.

Styles can be locally scoped to avoid globally scoping styles.

The syntax :local(.className) can be used to declare className in the local scope. The local identifiers are exported by the module.

With :local (without brackets) local mode can be switched on for this selector. The :global(.className) notation can be used to declare an explicit global selector. With :global (without brackets) global mode can be switched on for this selector.

The loader replaces local selectors with unique identifiers. The chosen unique identifiers are exported by the module.

:local(.className) {
  background: red;
}
:local .className {
  color: green;
}
:local(.className .subClass) {
  color: green;
}
:local .className .subClass :global(.global-class-name) {
  color: blue;
}

._23_aKvs-b8bW2Vg3fwHozO {
  background: red;
}
._23_aKvs-b8bW2Vg3fwHozO {
  color: green;
}
._23_aKvs-b8bW2Vg3fwHozO ._13LGdX8RMStbBE9w-t0gZ1 {
  color: green;
}
._23_aKvs-b8bW2Vg3fwHozO ._13LGdX8RMStbBE9w-t0gZ1 .global-class-name {
  color: blue;
}

ℹ️ Identifiers are exported

exports.locals = {
  className: '_23_aKvs-b8bW2Vg3fwHozO',
  subClass: '_13LGdX8RMStbBE9w-t0gZ1',
};

CamelCase is recommended for local selectors. They are easier to use within the imported JS module.

You can use :local(#someId), but this is not recommended. Use classes instead of ids.

`Composing`

When declaring a local classname you can compose a local class from another local classname.

:local(.className) {
  background: red;
  color: yellow;
}

:local(.subClass) {
  composes: className;
  background: blue;
}

This doesn't result in any change to the CSS itself but exports multiple classnames.

exports.locals = {
  className: '_23_aKvs-b8bW2Vg3fwHozO',
  subClass: '_13LGdX8RMStbBE9w-t0gZ1 _23_aKvs-b8bW2Vg3fwHozO',
};

._23_aKvs-b8bW2Vg3fwHozO {
  background: red;
  color: yellow;
}

._13LGdX8RMStbBE9w-t0gZ1 {
  background: blue;
}

`Importing`

To import a local classname from another module.

:local(.continueButton) {
  composes: button from 'library/button.css';
  background: red;
}

:local(.nameEdit) {
  composes: edit highlight from './edit.css';
  background: red;
}

To import from multiple modules use multiple composes: rules.

:local(.className) {
  composes: edit hightlight from './edit.css';
  composes: button from 'module/button.css';
  composes: classFromThisModule;
  background: red;
}

`Values`

You can use @value to specific values to be reused throughout a document.

We recommend use prefix v- for values, s- for selectors and m- for media at-rules.

@value v-primary: #BF4040;
@value s-black: black-selector;
@value m-large: (min-width: 960px);

.header {
  color: v-primary;
  padding: 0 10px;
}

.s-black {
  color: black;
}

@media m-large {
  .header {
    padding: 0 20px;
  }
}

`Boolean`

Enable CSS Modules features.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          modules: true,
        },
      },
    ],
  },
};

`String`

Enable CSS Modules features and setup mode.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          // Using `local` value has same effect like using `modules: true`
          modules: 'global',
        },
      },
    ],
  },
};

`Object`

Enable CSS Modules features and setup options for them.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          modules: {
            mode: 'local',
            exportGlobals: true,
            localIdentName: '[path][name]__[local]--[hash:base64:5]',
            context: path.resolve(__dirname, 'src'),
            hashPrefix: 'my-custom-hash',
          },
        },
      },
    ],
  },
};

`auto`

Type: Boolean|RegExp Default: 'undefined'

Allows auto enable css modules based on filename.

`Boolean`

Possible values:

true - enable css modules for all files for which /\.module\.\w+$/i.test(filename) return true
false - disable css modules

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          modules: {
            auto: true,
          },
        },
      },
    ],
  },
};

`RegExp`

Enable css modules for files based on a filename and satisfying your regex.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          modules: {
            auto: /\.custom-module\.\w+$/i,
          },
        },
      },
    ],
  },
};

`mode`

Type: String|Function Default: 'local'

Setup mode option. You can omit the value when you want local mode.

`String`

Possible values - local, global, and pure.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          modules: {
            mode: 'global',
          },
        },
      },
    ],
  },
};

`Function`

Allows set different values for the mode option based on a filename

Possible return values - local, global, and pure.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          modules: {
            // Callback must return "local", "global", or "pure" values
            mode: (resourcePath) => {
              if (/pure.css$/i.test(resourcePath)) {
                return 'pure';
              }

              if (/global.css$/i.test(resourcePath)) {
                return 'global';
              }

              return 'local';
            },
          },
        },
      },
    ],
  },
};

`exportGlobals`

Type: Boolean Default: false

Allow css-loader to export names from global class or id, so you can use that as local name.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          modules: {
            exportGlobals: true,
          },
        },
      },
    ],
  },
};

`localIdentName`

Type: String Default: '[hash:base64]'

You can configure the generated ident with the localIdentName query parameter. See loader-utils's documentation for more information on options.

Recommendations:

use '[path][name]__[local]' for development
use '[hash:base64]' for production

The [local] placeholder contains original class.

Note: all reserved (<>:"/\|?*) and control filesystem characters (excluding characters in the [local] placeholder) will be converted to -.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          modules: {
            localIdentName: '[path][name]__[local]--[hash:base64:5]',
          },
        },
      },
    ],
  },
};

`context`

Type: String Default: undefined

Allow to redefine basic loader context for local ident name. By default we use rootContext of loader.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          modules: {
            context: path.resolve(__dirname, 'context'),
          },
        },
      },
    ],
  },
};

`hashPrefix`

Type: String Default: undefined

Allow to add custom hash to generate more unique classes.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          modules: {
            hashPrefix: 'hash',
          },
        },
      },
    ],
  },
};

`getLocalIdent`

Type: Function Default: undefined

You can also specify the absolute path to your custom getLocalIdent function to generate classname based on a different schema. By default we use built-in function to generate a classname.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          modules: {
            getLocalIdent: (context, localIdentName, localName, options) => {
              return 'whatever_random_class_name';
            },
          },
        },
      },
    ],
  },
};

`localIdentRegExp`

Type: String|RegExp Default: undefined

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          modules: {
            localIdentRegExp: /page-(.*)\.css/i,
          },
        },
      },
    ],
  },
};

`sourceMap`

Type: Boolean Default: false

Enables/Disables generation of source maps.

To include source maps set the sourceMap option.

They are not enabled by default because they expose a runtime overhead and increase in bundle size (JS source maps do not).

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          sourceMap: true,
        },
      },
    ],
  },
};

`importLoaders`

Type: Number Default: 0

Enables/Disables or setups number of loaders applied before CSS loader.

The option importLoaders allows you to configure how many loaders before css-loader should be applied to @imported resources.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        use: [
          'style-loader',
          {
            loader: 'css-loader',
            options: {
              importLoaders: 2,
              // 0 => no loaders (default);
              // 1 => postcss-loader;
              // 2 => postcss-loader, sass-loader
            },
          },
          'postcss-loader',
          'sass-loader',
        ],
      },
    ],
  },
};

This may change in the future when the module system (i. e. webpack) supports loader matching by origin.

`localsConvention`

Type: String Default: 'asIs'

Style of exported classnames.

By default, the exported JSON keys mirror the class names (i.e asIs value).

Name	Type	Description
Name Type Description `'asIs'` `{String}`	`{String}`	Class names will be exported as is.
Name Type Description `'camelCase'` `{String}`	`{String}`	Class names will be camelized, the original class name will not to be removed from the locals
Name Type Description `'camelCaseOnly'` `{String}`	`{String}`	Class names will be camelized, the original class name will be removed from the locals
Name Type Description `'dashes'` `{String}`	`{String}`	Only dashes in class names will be camelized
Name Type Description `'dashesOnly'` `{String}`	`{String}`	Dashes in class names will be camelized, the original class name will be removed from the locals

file.css

.class-name {
}

file.js

import { className } from 'file.css';

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          localsConvention: 'camelCase',
        },
      },
    ],
  },
};

`onlyLocals`

Type: Boolean Default: false

Export only locals.

Useful when you use css modules for pre-rendering (for example SSR). For pre-rendering with mini-css-extract-plugin you should use this option instead of style-loader!css-loader in the pre-rendering bundle. It doesn't embed CSS but only exports the identifier mappings.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: 'css-loader',
        options: {
          onlyLocals: true,
        },
      },
    ],
  },
};

`esModule`

Type: Boolean Default: false

By default, css-loader 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

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

Examples

Assets

The following webpack.config.js can load CSS files, embed small PNG/JPG/GIF/SVG images as well as fonts as Data URLs and copy larger files to the output directory.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        use: ['style-loader', 'css-loader'],
      },
      {
        test: /\.(png|jpe?g|gif|svg|eot|ttf|woff|woff2)$/i,
        loader: 'url-loader',
        options: {
          limit: 8192,
        },
      },
    ],
  },
};

Extract

For production builds it's recommended to extract the CSS from your bundle being able to use parallel loading of CSS/JS resources later on.

This can be achieved by using the mini-css-extract-plugin to extract the CSS when running in production mode.
As an alternative, if seeking better development performance and css outputs that mimic production. extract-css-chunks-webpack-plugin offers a hot module reload friendly, extended version of mini-css-extract-plugin. HMR real CSS files in dev, works like mini-css in non-dev

Pure CSS, CSS modules and PostCSS

When you have pure CSS (without CSS modules), CSS modules and PostCSS in your project you can use this setup:

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        // For CSS modules
        // For pure CSS - /\.css$/i,
        // For Sass/SCSS - /\.((c|sa|sc)ss)$/i,
        // For Less - /\.((c|le)ss)$/i,
        test: /\.((c|sa|sc)ss)$/i,
        use: [
          'style-loader',
          {
            loader: 'css-loader',
            options: {
              // Run `postcss-loader` on each CSS `@import`, do not forget that `sass-loader` compile non CSS `@import`'s into a single file
              // If you need run `sass-loader` and `postcss-loader` on each CSS `@import` please set it to `2`
              importLoaders: 1,
              // Automatically enable css modules for files satisfying `/\.module\.\w+$/i` RegExp.
              modules: { auto: true },
            },
          },
          {
            loader: 'postcss-loader',
            options: { plugins: () => [postcssPresetEnv({ stage: 0 })] },
          },
          // Can be `less-loader`
          // The `test` property should be `\.less/i`
          {
            test: /\.s[ac]ss$/i,
            loader: 'sass-loader',
          },
        ],
      },
      {
        test: /\.(png|jpe?g|gif|svg|eot|ttf|woff|woff2)$/i,
        loader: 'url-loader',
        options: {
          limit: 8192,
        },
      },
    ],
  },
};

Contributing

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

CONTRIBUTING

License

MIT