css-loader

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

Getting Started

⚠ To use css-loader, webpack@5 is required

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"],
      },
    ],
  },
};

And run webpack via your preferred method.

If, for one reason or another, you need to extract CSS as a file (i.e. do not store CSS in a JS module) you might want to check out the recommend example.

Options

Name	Type	Default	Description
`url`	`{Boolean\|Object}`	`true`	Allows to enables/disables `url()`/`image-set()` functions handling
`import`	`{Boolean\|Object}`	`true`	Allows to enables/disables `@import` at-rules handling
`modules`	`{Boolean\|String\|Object}`	`{auto: true}`	Allows to enables/disables or setup CSS Modules options
`sourceMap`	`{Boolean}`	`compiler.devtool`	Enables/Disables generation of source maps
`importLoaders`	`{Number}`	`0`	Allows enables/disables or setups number of loaders applied before CSS loader for `@import`/CSS Modules and ICSS imports
`esModule`	`{Boolean}`	`true`	Use ES modules syntax
`exportType`	`{'array' \| 'string' \| 'css-style-sheet'}`	`array`	Allows exporting styles as array with modules, string or constructable stylesheet (i.e. `CSSStyleSheet`)

`url`

Type: Boolean|Object Default: true

Allow to enable/disables handling the CSS functions url and image-set. If set to false, css-loader will not parse any paths specified in url or image-set. A function can also be passed to control this behavior dynamically based on the path to the asset. Starting with version 4.0.0, absolute paths are parsed based on the server root.

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,
        },
      },
    ],
  },
};

`Object`

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: {
            filter: (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|Object Default: true

Allows to 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,
        },
      },
    ],
  },
};

`Object`

Name	Type	Default	Description
`filter`	`{Function}`	`undefined`	Allow to filter `@import`

`filter`

Type: Function Default: undefined

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: {
            filter: (url, media, resourcePath) => {
              // resourcePath - path to css file

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

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

`modules`

Type: Boolean|String|Object Default: undefined

Allows to enable/disable CSS Modules or ICSS and setup configuration:

undefined - enable CSS modules for all files matching /\.module\.\w+$/i.test(filename) and /\.icss\.\w+$/i.test(filename) regexp.
true - enable CSS modules for all files.
false - disables CSS Modules for all files.
string - disables CSS Modules for all files and set the mode option, more information you can read here
object - enable CSS modules for all files, if modules.auto option is not specified, otherwise the modules.auto option will determine whether if it is CSS modules or not, more information you can read here

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.

i We strongly recommend that you specify the extension when importing a file, since it is possible to import a file with any extension and it is not known in advance which file to use.

: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",
            auto: true,
            exportGlobals: true,
            localIdentName: "[path][name]__[local]--[hash:base64:5]",
            localIdentContext: path.resolve(__dirname, "src"),
            localIdentHashSalt: "my-custom-hash",
            namedExport: true,
            exportLocalsConvention: "camelCase",
            exportOnlyLocals: false,
          },
        },
      },
    ],
  },
};

`auto`

Type: Boolean|RegExp|Function Default: undefined

Allows auto enable CSS modules/ICSS based on filename when modules option is object.

Possible values:

undefined - enable CSS modules for all files.
true - enable CSS modules for all files matching /\.module\.\w+$/i.test(filename) and /\.icss\.\w+$/i.test(filename) regexp.
false - disables CSS Modules.
RegExp - enable CSS modules for all files matching /RegExp/i.test(filename) regexp.
function - enable CSS Modules for files based on the filename satisfying your filter function check.

`Boolean`

Possible values:

true - enables CSS modules or interoperable CSS format, sets the modules.mode option to local value for all files which satisfy /\.module(s)?\.\w+$/i.test(filename) condition or sets the modules.mode option to icss value for all files which satisfy /\.icss\.\w+$/i.test(filename) condition
false - disables CSS modules or interoperable CSS format based on filename

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 the filename satisfying your regex check.

webpack.config.js

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

`Function`

Enable css modules for files based on the filename satisfying your filter function check.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: "css-loader",
        options: {
          modules: {
            auto: (resourcePath) => resourcePath.endsWith(".custom-module.css"),
          },
        },
      },
    ],
  },
};

`mode`

Type: String|Function Default: 'local'

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

Controls the level of compilation applied to the input styles.

The local, global, and pure handles class and id scoping and @value values. The icss will only compile the low level Interoperable CSS format for declaring :import and :export dependencies between CSS and other languages.

ICSS underpins CSS Module support, and provides a low level syntax for other tools to implement CSS-module variations of their own.

`String`

Possible values - local, global, pure, and icss.

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, pure and icss.

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";
            },
          },
        },
      },
    ],
  },
};

`localIdentName`

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

Allows to configure the generated local ident name.

For more information on options see:

webpack template strings,
output.hashDigest,
output.hashDigestLength,
output.hashFunction,
output.hashSalt.

Supported template strings:

[name] the basename of the resource
[folder] the folder the resource relative to the compiler.context option or modules.localIdentContext option.
[path] the path of the resource relative to the compiler.context option or modules.localIdentContext option.
[file] - filename and path.
[ext] - extension with leading ..
[hash] - the hash of the string, generated based on localIdentHashSalt, localIdentHashFunction, localIdentHashDigest, localIdentHashDigestLength, localIdentContext, resourcePath and exportName
[<hashFunction>#⃣<hashDigest>:<hashDigestLength>] - hash with hash settings.
[local] - original class.

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]",
          },
        },
      },
    ],
  },
};

`localIdentContext`

Type: String Default: compiler.context

Allows to redefine basic loader context for local ident name.

webpack.config.js

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

`localIdentHashSalt`

Type: String Default: undefined

Allows to add custom hash to generate more unique classes. For more information see output.hashSalt.

webpack.config.js

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

`localIdentHashFunction`

Type: String Default: md4

Allows to specify hash function to generate classes . For more information see output.hashFunction.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: "css-loader",
        options: {
          modules: {
            localIdentHashFunction: "md4",
          },
        },
      },
    ],
  },
};

`localIdentHashDigest`

Type: String Default: hex

Allows to specify hash digest to generate classes. For more information see output.hashDigest.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: "css-loader",
        options: {
          modules: {
            localIdentHashDigest: "base64",
          },
        },
      },
    ],
  },
};

`localIdentHashDigestLength`

Type: Number Default: 20

Allows to specify hash digest length to generate classes. For more information see output.hashDigestLength.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: "css-loader",
        options: {
          modules: {
            localIdentHashDigestLength: 5,
          },
        },
      },
    ],
  },
};

`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,
          },
        },
      },
    ],
  },
};

`getLocalIdent`

Type: Function Default: undefined

Allows to specify a function to generate the classname. By default we use built-in function to generate a classname. If the custom function returns null or undefined, we fallback to the built-in function to generate the 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";
            },
          },
        },
      },
    ],
  },
};

`namedExport`

Type: Boolean Default: false

Enables/disables ES modules named export for locals.

⚠ Names of locals are converted to camelcase, i.e. the exportLocalsConvention option has camelCaseOnly value by default.

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

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

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

To set a custom name for namedExport, can use exportLocalsConvention option as a function. Example below in the examples section.

`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,
          },
        },
      },
    ],
  },
};

`exportLocalsConvention`

Type: String|Function Default: based on the modules.namedExport option value, if true - camelCaseOnly, otherwise asIs

Style of exported class names.

`String`

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

⚠ Only camelCaseOnly value allowed if you set the namedExport value to true.

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

`Function`

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: "css-loader",
        options: {
          modules: {
            exportLocalsConvention: function (name) {
              return name.replace(/-/g, "_");
            },
          },
        },
      },
    ],
  },
};

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: "css-loader",
        options: {
          modules: {
            exportLocalsConvention: function (name) {
              return [
                name.replace(/-/g, "_"),
                // dashesCamelCase
                name.replace(/-+(\w)/g, (match, firstLetter) =>
                  firstLetter.toUpperCase()
                ),
              ];
            },
          },
        },
      },
    ],
  },
};

`exportOnlyLocals`

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: {
          modules: {
            exportOnlyLocals: true,
          },
        },
      },
    ],
  },
};

`importLoaders`

Type: Number Default: 0

Allows to enables/disables or setups number of loaders applied before CSS loader for @import at-rules, CSS modules and ICSS imports, i.e. @import/composes/@value value from './values.css'/etc.

The option importLoaders allows you to configure how many loaders before css-loader should be applied to @imported resources and CSS modules/ICSS imports.

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.

`sourceMap`

Type: Boolean Default: depends on the compiler.devtool value

By default generation of source maps depends on the devtool option. All values enable source map generation except eval and false value.

webpack.config.js

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

`esModule`

Type: Boolean Default: true

By default, css-loader 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 modules syntax using:

webpack.config.js

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

`exportType`

Type: 'array' | 'string' | 'css-style-sheet' Default: 'array'

Allows exporting styles as array with modules, string or constructable stylesheet (i.e. CSSStyleSheet). Default value is 'array', i.e. loader exports array of modules with specific API which is used in style-loader or other.

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        assert: { type: "css" },
        loader: "css-loader",
        options: {
          exportType: "css-style-sheet",
        },
      },
    ],
  },
};

src/index.js

import sheet from "./styles.css" assert { type: "css" };

document.adoptedStyleSheets = [sheet];
shadowRoot.adoptedStyleSheets = [sheet];

`'array'`

The default export is array of modules with specific API which is used in style-loader or other.

webpack.config.js

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

src/index.js

// `style-loader` applies styles to DOM
import "./styles.css";

`'string'`

⚠ You don't need style-loader anymore, please remove it. ⚠ The esModules option should be enabled if you want to use it with CSS modules, by default for locals will be used named export.

The default export is string.

webpack.config.js

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

src/index.js

import sheet from "./styles.css";

console.log(sheet);

`'css-style-sheet'`

⚠ @import rules not yet allowed, more information ⚠ You don't need style-loader anymore, please remove it. ⚠ The esModules option should be enabled if you want to use it with CSS modules, by default for locals will be used named export. ⚠ Source maps are not currently supported in Chrome due bug

The default export is a constructable stylesheet (i.e. CSSStyleSheet).

Useful for custom elements and shadow DOM.

More information:

Using CSS Module Scripts to import stylesheets
Constructable Stylesheets: seamless reusable styles

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        assert: { type: "css" },
        loader: "css-loader",
        options: {
          exportType: "css-style-sheet",
        },
      },

      // For Sass/SCSS:
      //
      // {
      //   assert: { type: "css" },
      //   rules: [
      //     {
      //       loader: "css-loader",
      //       options: {
      //         exportType: "css-style-sheet",
      //         // Other options
      //       },
      //     },
      //     {
      //       loader: "sass-loader",
      //       options: {
      //         // Other options
      //       },
      //     },
      //   ],
      // },
    ],
  },
};

src/index.js

// Example for Sass/SCSS:
// import sheet from "./styles.scss" assert { type: "css" };

// Example for CSS modules:
// import sheet, { myClass } from "./styles.scss" assert { type: "css" };

// Example for CSS:
import sheet from "./styles.css" assert { type: "css" };

document.adoptedStyleSheets = [sheet];
shadowRoot.adoptedStyleSheets = [sheet];

For migration purposes, you can use the following configuration:

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        oneOf: [
          {
            assert: { type: "css" },
            loader: "css-loader",
            options: {
              exportType: "css-style-sheet",
              // Other options
            },
          },
          {
            use: [
              "style-loader",
              {
                loader: "css-loader",
                options: {
                  // Other options
                },
              },
            ],
          },
        ],
      },
    ],
  },
};

Examples

Recommend

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, because it creates separate css files. For development mode (including webpack-dev-server) you can use style-loader, because it injects CSS into the DOM using multiple <style></style> 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";

module.exports = {
  module: {
    rules: [
      {
        test: /\.(sa|sc|c)ss$/i,
        use: [
          devMode ? "style-loader" : MiniCssExtractPlugin.loader,
          "css-loader",
          "postcss-loader",
          "sass-loader",
        ],
      },
    ],
  },
  plugins: [].concat(devMode ? [] : [new MiniCssExtractPlugin()]),
};

Disable url resolving using the `/* webpackIgnore: true */` comment

With the help of the /* webpackIgnore: true */comment, it is possible to disable sources handling for rules and for individual declarations.

/* webpackIgnore: true */
@import url(./basic.css);
@import /* webpackIgnore: true */ url(./imported.css);

.class {
  /* Disabled url handling for the all urls in the 'background' declaration */
  color: red;
  /* webpackIgnore: true */
  background: url("./url/img.png"), url("./url/img.png");
}

.class {
  /* Disabled url handling for the first url in the 'background' declaration */
  color: red;
  background: 
    /* webpackIgnore: true */ url("./url/img.png"), url("./url/img.png");
}

.class {
  /* Disabled url handling for the second url in the 'background' declaration */
  color: red;
  background: url("./url/img.png"),
    /* webpackIgnore: true */ url("./url/img.png");
}

/* prettier-ignore */
.class {
  /* Disabled url handling for the second url in the 'background' declaration */
  color: red;
  background: url("./url/img.png"),
    /* webpackIgnore: true */ 
    url("./url/img.png");
}

/* prettier-ignore */
.class {
  /* Disabled url handling for third and sixth urls in the 'background-image' declaration */
  background-image: image-set(
    url(./url/img.png) 2x,
    url(./url/img.png) 3x,
    /* webpackIgnore:  true */ url(./url/img.png) 4x,
    url(./url/img.png) 5x,
    url(./url/img.png) 6x,
    /* webpackIgnore:  true */
    url(./url/img.png) 7x
  );
}

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.

For webpack v5:

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,
        // More information here https://webpack.js.org/guides/asset-modules/
        type: "asset",
      },
    ],
  },
};

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 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` and CSS modules/ICSS imports, 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,
            },
          },
          {
            loader: "postcss-loader",
            options: { plugins: () => [postcssPresetEnv({ stage: 0 })] },
          },
          // Can be `less-loader`
          {
            loader: "sass-loader",
          },
        ],
      },
      // For webpack v5
      {
        test: /\.(png|jpe?g|gif|svg|eot|ttf|woff|woff2)$/i,
        // More information here https://webpack.js.org/guides/asset-modules/
        type: "asset",
      },
    ],
  },
};

Resolve unresolved URLs using an alias

index.css

.class {
  background: url(/assets/unresolved/img.png);
}

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        use: ["style-loader", "css-loader"],
      },
    ],
  },
  resolve: {
    alias: {
      "/assets/unresolved/img.png": path.resolve(
        __dirname,
        "assets/real-path-to-img/img.png"
      ),
    },
  },
};

Named export with custom export names

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/i,
        loader: "css-loader",
        options: {
          modules: {
            namedExport: true,
            exportLocalsConvention: function (name) {
              return name.replace(/-/g, "_");
            },
          },
        },
      },
    ],
  },
};

Separating `Interoperable CSS`-only and `CSS Module` features

The following setup is an example of allowing Interoperable CSS features only (such as :import and :export) without using further CSS Module functionality by setting mode option for all files that do not match *.module.scss naming convention. This is for reference as having ICSS features applied to all files was default css-loader behavior before v4. Meanwhile all files matching *.module.scss are treated as CSS Modules in this example.

An example case is assumed where a project requires canvas drawing variables to be synchronized with CSS - canvas drawing uses the same color (set by color name in JavaScript) as HTML background (set by class name in CSS).

webpack.config.js

module.exports = {
  module: {
    rules: [
      // ...
      // --------
      // SCSS ALL EXCEPT MODULES
      {
        test: /\.scss$/i,
        exclude: /\.module\.scss$/i,
        use: [
          {
            loader: "style-loader",
          },
          {
            loader: "css-loader",
            options: {
              importLoaders: 1,
              modules: {
                mode: "icss",
              },
            },
          },
          {
            loader: "sass-loader",
          },
        ],
      },
      // --------
      // SCSS MODULES
      {
        test: /\.module\.scss$/i,
        use: [
          {
            loader: "style-loader",
          },
          {
            loader: "css-loader",
            options: {
              importLoaders: 1,
              modules: {
                mode: "local",
              },
            },
          },
          {
            loader: "sass-loader",
          },
        ],
      },
      // --------
      // ...
    ],
  },
};

variables.scss

File treated as ICSS-only.

$colorBackground: red;
:export {
  colorBackgroundCanvas: $colorBackground;
}

Component.module.scss

File treated as CSS Module.

@import "variables.scss";
.componentClass {
  background-color: $colorBackground;
}

Component.jsx

Using both CSS Module functionality as well as SCSS variables directly in JavaScript.

import svars from "variables.scss";
import styles from "Component.module.scss";

// Render DOM with CSS modules class name
// <div className={styles.componentClass}>
//   <canvas ref={mountsCanvas}/>
// </div>

// Somewhere in JavaScript canvas drawing code use the variable directly
// const ctx = mountsCanvas.current.getContext('2d',{alpha: false});
ctx.fillStyle = `${svars.colorBackgroundCanvas}`;

Contributing

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

CONTRIBUTING

License

MIT

css-loaderCSS Loader

css-loader

Getting Started

Options

url

Boolean

Object

import

Boolean

Object

filter

modules

Features

Scope

Composing

Importing

Values

Boolean

String

Object

auto

Boolean

RegExp

Function

mode

String

Function

localIdentName

localIdentContext

localIdentHashSalt

localIdentHashFunction

localIdentHashDigest

localIdentHashDigestLength

localIdentRegExp

getLocalIdent

namedExport

exportGlobals

exportLocalsConvention

String

Function

exportOnlyLocals

importLoaders

sourceMap

esModule

exportType

'array'

'string'

'css-style-sheet'

Examples

Recommend

Disable url resolving using the /* webpackIgnore: true */ comment

Assets

Extract

Pure CSS, CSS modules and PostCSS

Resolve unresolved URLs using an alias

Named export with custom export names

Separating Interoperable CSS-only and CSS Module features

Contributing

License

`url`

`Boolean`

`Object`

`import`

`Boolean`

`Object`

`filter`

`modules`

`Features`

`Scope`

`Composing`

`Importing`

`Values`

`Boolean`

`String`

`Object`

`auto`

`Boolean`

`RegExp`

`Function`

`mode`

`String`

`Function`

`localIdentName`

`localIdentContext`

`localIdentHashSalt`

`localIdentHashFunction`

`localIdentHashDigest`

`localIdentHashDigestLength`

`localIdentRegExp`

`getLocalIdent`

`namedExport`

`exportGlobals`

`exportLocalsConvention`

`String`

`Function`

`exportOnlyLocals`

`importLoaders`

`sourceMap`

`esModule`

`exportType`

`'array'`

`'string'`

`'css-style-sheet'`

Disable url resolving using the `/* webpackIgnore: true */` comment

Separating `Interoperable CSS`-only and `CSS Module` features