README

# 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.

### <tt>toString</tt>

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'],
},
],
},
};

or

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
--- | --- | --- | ---
**`url`** | `{Boolean\|Function}` | `true` | Enables/Disables `url`/`image-set` functions handling
**`import`** | `{Boolean\|Function}` | `true` | Enables/Disables `@import` at-rules handling
**`modules`** | `{Boolean\|String\|Object}` | `{auto: true}` | Enables/Disables CSS Modules and their configuration
**`sourceMap`** | `{Boolean}` | `compiler.devtool` | Enables/Disables generation of source maps
**`importLoaders`** | `{Number}` | `0` | Enables/Disables or setups number of loaders applied before CSS loader
**`esModule`** | `{Boolean}` | `true` | Use ES modules syntax

### <tt>url</tt>

Type: `Boolean|Function` Default: `true`

Enables/Disables `url`/`image-set` functions handling. Control `url()` resolving. Absolute 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')

#### <tt>Boolean</tt>

Enable/disable `url()` resolving.

webpack.config.js

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

#### <tt>Function</tt>

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

### <tt>import</tt>

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')

#### <tt>Boolean</tt>

Enable/disable `@import` resolving.

webpack.config.js

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

#### <tt>Function</tt>

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: (url, media, resourcePath) => {
// resourcePath - path to css file
// Don't handle `style.css` import
if (url.includes('style.css')) {
return false;
}
return true;
},
},
},
],
},
};

### <tt>modules</tt>

Type: `Boolean|String|Object` Default: based on filename, `true` for all files matching `/\.module\.\w+$/i.test(filename)` regular expression, more information you can read here

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,
},
},
],
},
};

#### <tt>Features</tt>

##### `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;
}
}

#### <tt>Boolean</tt>

Enable CSS Modules features.

webpack.config.js

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

#### <tt>String</tt>

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',
},
},
],
},
};

#### <tt>Object</tt>

Enable CSS Modules features and setup options for them.

webpack.config.js

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

##### `compileType`

Type: ‘'module’ | 'icss'`Default:`'module'`

Controls the level of compilation applied to the input styles.

The `module` 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.

webpack.config.js

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

##### `auto`

Type: `Boolean|RegExp|Function` Default: ‘'true’`

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 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.

###### `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';
},
},
},
},
],
},
};

##### `localIdentName`

Type: `String` Default: ‘’[hash:base64]'`

Allows to configure the generated local ident name. 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]',
},
},
},
],
},
};

##### `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: {
context: path.resolve(__dirname, 'context'),
},
},
},
],
},
};

##### `localIdentHashPrefix`

Type: `String` Default: `undefined`

Allows to add custom hash to generate more unique classes.

webpack.config.js

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

##### `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.

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

##### `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` Default: based on the `modules.namedExport` option value, if `true` - `camelCaseOnly`, otherwise `asIs`

Style of exported class names.

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’`** \ilinebr </td> <td class="markdownTableBodyCenter">`{String}`\ilinebr </td> <td class="markdownTableBodyLeft"> Class names will be exported as is. \ilinebr </td> </tr> <tr class="markdownTableRowEven"> <td class="markdownTableBodyCenter"> **`'camelCase'`** \ilinebr </td> <td class="markdownTableBodyCenter">`{String}`\ilinebr </td> <td class="markdownTableBodyLeft"> Class names will be camelized, the original class name will not to be removed from the locals \ilinebr </td> </tr> <tr class="markdownTableRowOdd"> <td class="markdownTableBodyCenter"> **`'camelCaseOnly'`** \ilinebr </td> <td class="markdownTableBodyCenter">`{String}`\ilinebr </td> <td class="markdownTableBodyLeft"> Class names will be camelized, the original class name will be removed from the locals \ilinebr </td> </tr> <tr class="markdownTableRowEven"> <td class="markdownTableBodyCenter"> **`'dashes'`** \ilinebr </td> <td class="markdownTableBodyCenter">`{String}`\ilinebr </td> <td class="markdownTableBodyLeft"> Only dashes in class names will be camelized \ilinebr </td> </tr> <tr class="markdownTableRowOdd"> <td class="markdownTableBodyCenter"> **`'dashesOnly'`** \ilinebr </td> <td class="markdownTableBodyCenter">`{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: {
mode: 'local',
localsConvention: 'camelCase',
},
},
],
},
};

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

### <tt>sourceMap</tt>

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,
},
},
],
},
};

### <tt>importLoaders</tt>

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 `@import`ed 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.

### <tt>esModule</tt>

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,
},
},
],
},
};

## 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 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+$/i` RegExp.
modules: { auto: true },
},
},
{
loader: 'postcss-loader',
options: { plugins: () => [postcssPresetEnv({ stage: 0 })] },
},
// Can be `less-loader`
{
loader: 'sass-loader',
},
],
},
{
test: /\.(png|jpe?g|gif|svg|eot|ttf|woff|woff2)$/i,
loader: 'url-loader',
options: {
limit: 8192,
},
},
],
},
};

### 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'
),
},
},
};

### Separating <tt>Interoperable CSS</tt>-only and <tt>CSS Module</tt> 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 `compileType` 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$/,
exclude: /\.module\.scss$/,
use: [
{
loader: 'style-loader'
},
{
loader: 'css-loader',
options: {
importLoaders: 1,
modules: {
compileType: 'icss'
}
}
},
{
loader: 'sass-loader'
},
],
},
// --------
// SCSS MODULES
{
test: /\.module\.scss$/,
use: [
{
loader: 'style-loader'
},
{
loader: 'css-loader',
options: {
importLoaders: 1,
modules: {
compileType: 'module'
}
}
},
{
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.

./.github/CONTRIBUTING.md "CONTRIBUTING"

## License

MIT