The css-loader interprets @import and url() like import/require() and will resolve them.
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$/i,
use: ["style-loader", "css-loader"],
},
],
},
}; Only for webpack v4:
Good loaders for requiring your assets are the file-loader and the url-loader which you should specify in your config (see below).
And run webpack via your preferred method.
toStringYou can also use the css-loader results directly as a string, such as in Angular's component style.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/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$/i,
use: [
"handlebars-loader", // handlebars loader expects raw resource string
"extract-loader",
"css-loader",
],
},
],
},
}; | Name | Type | Default | Description |
|---|---|---|---|
url | {Boolean|Function} | true | Enables/Disables url/image-set functions handling |
import | {Boolean|Function} | true | Enables/Disables @import at-rules handling |
modules | {Boolean|String|Object} | {auto: true} | Enables/Disables CSS Modules and their configuration |
sourceMap | {Boolean} | compiler.devtool | Enables/Disables generation of source maps |
importLoaders | {Number} | 0 | Enables/Disables or setups number of loaders applied before CSS loader |
esModule | {Boolean} | true | Use ES modules syntax |
urlType: Boolean|Function Default: true
Enables/Disables url/image-set functions handling. Control url() resolving. Absolute paths and root-relative URLs now resolving(Version 4.0.0 and above).
Examples resolutions:
url(image.png) => require('./image.png')
url('image.png') => require('./image.png')
url(./image.png) => require('./image.png')
url('./image.png') => require('./image.png')
url('http://dontwritehorriblecode.com/2112.png') => require('http://dontwritehorriblecode.com/2112.png')
image-set(url('image2x.png') 1x, url('image1x.png') 2x) => require('./image1x.png') and require('./image2x.png')
To import assets from a node_modules path (include resolve.modules) and for alias, prefix it with a ~:
url(~module/image.png) => require('module/image.png')
url('~module/image.png') => require('module/image.png')
url(~aliasDirectory/image.png) => require('otherDirectory/image.png')
BooleanEnable/disable url() resolving.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
url: true,
},
},
],
},
}; FunctionAllow 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$/i,
loader: "css-loader",
options: {
url: (url, resourcePath) => {
// resourcePath - path to css file
// Don't handle `img.png` urls
if (url.includes("img.png")) {
return false;
}
return true;
},
},
},
],
},
}; importType: Boolean|Function Default: true
Enables/Disables @import at-rules handling. Control @import resolving. Absolute urls in @import will be moved in runtime code.
Examples resolutions:
@import 'style.css' => require('./style.css')
@import url(style.css) => require('./style.css')
@import url('style.css') => require('./style.css')
@import './style.css' => require('./style.css')
@import url(./style.css) => require('./style.css')
@import url('./style.css') => require('./style.css')
@import url('http://dontwritehorriblecode.com/style.css') => @import url('http://dontwritehorriblecode.com/style.css') in runtime
To import styles from a node_modules path (include resolve.modules) and for alias, prefix it with a ~:
@import url(~module/style.css) => require('module/style.css')
@import url('~module/style.css') => require('module/style.css')
@import url(~aliasDirectory/style.css) => require('otherDirectory/style.css')
BooleanEnable/disable @import resolving.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
import: true,
},
},
],
},
}; FunctionAllow 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$/i,
loader: "css-loader",
options: {
import: (url, media, resourcePath) => {
// resourcePath - path to css file
// Don't handle `style.css` import
if (url.includes("style.css")) {
return false;
}
return true;
},
},
},
],
},
}; modulesType: Boolean|String|Object Default: based on filename, true for all files matching /\.module\.\w+$/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,
},
},
],
},
}; FeaturesScopeUsing 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.
ComposingWhen 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;
} ImportingTo 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;
} ValuesYou 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;
}
} BooleanEnable CSS Modules features.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: true,
},
},
],
},
}; StringEnable CSS Modules features and setup mode.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
// Using `local` value has same effect like using `modules: true`
modules: "global",
},
},
],
},
}; ObjectEnable CSS Modules features and setup options for them.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
compileType: "module",
mode: "local",
auto: true,
exportGlobals: true,
localIdentName: "[path][name]__[local]--[hash:base64:5]",
localIdentContext: path.resolve(__dirname, "src"),
localIdentHashPrefix: "my-custom-hash",
namedExport: true,
exportLocalsConvention: "camelCase",
exportOnlyLocals: false,
},
},
},
],
},
}; compileTypeType: '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$/i,
loader: "css-loader",
options: {
modules: {
compileType: "icss",
},
},
},
],
},
}; autoType: Boolean|RegExp|Function Default: 'true'
Allows auto enable CSS modules based on filename.
BooleanPossible values:
true - enables CSS modules or interoperable CSS format, sets the modules.compileType option to module value for all files which satisfy /\.module(s)?\.\w+$/i.test(filename) condition or sets the modules.compileType option to icss value for all files which satisfy /\.icss\.\w+$/i.test(filename) conditionfalse - disables CSS modules or interoperable CSS format based on filenamewebpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
auto: true,
},
},
},
],
},
}; RegExpEnable 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,
},
},
},
],
},
}; FunctionEnable css modules for files based on the filename satisfying your filter function check.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
auto: (resourcePath) => resourcePath.endsWith(".custom-module.css"),
},
},
},
],
},
}; modeType: String|Function Default: 'local'
Setup mode option. You can omit the value when you want local mode.
StringPossible values - local, global, and pure.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
mode: "global",
},
},
},
],
},
}; FunctionAllows 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$/i.test(resourcePath)) {
return "global";
}
return "local";
},
},
},
},
],
},
}; localIdentNameType: String Default: '[hash:base64]'
Allows to configure the generated local ident name. See loader-utils's documentation for more information on options.
Recommendations:
'[path][name]__[local]' for development'[hash:base64]' for productionThe [local] placeholder contains original class.
Note: all reserved (<>:"/\|?*) and control filesystem characters (excluding characters in the [local] placeholder) will be converted to -.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
localIdentName: "[path][name]__[local]--[hash:base64:5]",
},
},
},
],
},
}; localIdentContextType: String Default: compiler.context
Allows to redefine basic loader context for local ident name.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
localIdentContext: path.resolve(__dirname, "src"),
},
},
},
],
},
}; localIdentHashPrefixType: String Default: undefined
Allows to add custom hash to generate more unique classes.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
localIdentHashPrefix: "hash",
},
},
},
],
},
}; localIdentRegExpType: String|RegExp Default: undefined
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
localIdentRegExp: /page-(.*)\.css/i,
},
},
},
],
},
}; getLocalIdentType: Function Default: undefined
Allows to specify a function to generate the classname. By default we use built-in function to generate a classname. If the custom function returns null or undefined, we fallback to the built-in function to generate the classname.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
getLocalIdent: (context, localIdentName, localName, options) => {
return "whatever_random_class_name";
},
},
},
},
],
},
}; namedExportType: Boolean Default: false
Enables/disables ES modules named export for locals.
⚠ Names of locals are converted to camelcase, i.e. the
exportLocalsConventionoption hascamelCaseOnlyvalue 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$/i,
loader: "css-loader",
options: {
esModule: true,
modules: {
namedExport: true,
},
},
},
],
},
}; exportGlobalsType: Boolean Default: false
Allow css-loader to export names from global class or id, so you can use that as local name.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
exportGlobals: true,
},
},
},
],
},
}; exportLocalsConventionType: 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
camelCaseOnlyvalue allowed if you set thenamedExportvalue totrue.
| 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$/i,
loader: "css-loader",
options: {
modules: {
exportLocalsConvention: "camelCase",
},
},
},
],
},
}; exportOnlyLocalsType: Boolean Default: false
Export only locals.
Useful when you use css modules for pre-rendering (for example SSR). For pre-rendering with mini-css-extract-plugin you should use this option instead of style-loader!css-loader in the pre-rendering bundle. It doesn't embed CSS but only exports the identifier mappings.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
exportOnlyLocals: true,
},
},
},
],
},
}; sourceMapType: 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$/i,
loader: "css-loader",
options: {
sourceMap: true,
},
},
],
},
}; importLoadersType: Number Default: 0
Enables/Disables or setups number of loaders applied before CSS loader.
The option importLoaders allows you to configure how many loaders before css-loader should be applied to @imported resources.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/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.
esModuleType: 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$/i,
loader: "css-loader",
options: {
esModule: false,
},
},
],
},
}; The following webpack.config.js can load CSS files, embed small PNG/JPG/GIF/SVG images as well as fonts as Data URLs and copy larger files to the output directory.
For webpack v5:
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: ["style-loader", "css-loader"],
},
{
test: /\.(png|jpe?g|gif|svg|eot|ttf|woff|woff2)$/i,
// More information here https://webpack.js.org/guides/asset-modules/
type: "asset",
},
],
},
}; For webpack v4:
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: ["style-loader", "css-loader"],
},
{
test: /\.(png|jpe?g|gif|svg|eot|ttf|woff|woff2)$/i,
loader: "url-loader",
options: {
limit: 8192,
},
},
],
},
}; For production builds it's recommended to extract the CSS from your bundle being able to use parallel loading of CSS/JS resources later on.
This can be achieved by using the mini-css-extract-plugin to extract the CSS when running in production mode.
As an alternative, if seeking better development performance and css outputs that mimic production. extract-css-chunks-webpack-plugin offers a hot module reload friendly, extended version of mini-css-extract-plugin. HMR real CSS files in dev, works like mini-css in non-dev
When you have pure CSS (without CSS modules), CSS modules and PostCSS in your project you can use this setup:
webpack.config.js
module.exports = {
module: {
rules: [
{
// For pure CSS - /\.css$/i,
// For Sass/SCSS - /\.((c|sa|sc)ss)$/i,
// For Less - /\.((c|le)ss)$/i,
test: /\.((c|sa|sc)ss)$/i,
use: [
"style-loader",
{
loader: "css-loader",
options: {
// Run `postcss-loader` on each CSS `@import`, do not forget that `sass-loader` compile non CSS `@import`'s into a single file
// If you need run `sass-loader` and `postcss-loader` on each CSS `@import` please set it to `2`
importLoaders: 1,
},
},
{
loader: "postcss-loader",
options: { plugins: () => [postcssPresetEnv({ stage: 0 })] },
},
// Can be `less-loader`
{
loader: "sass-loader",
},
],
},
// For webpack v5
{
test: /\.(png|jpe?g|gif|svg|eot|ttf|woff|woff2)$/i,
// More information here https://webpack.js.org/guides/asset-modules/
type: "asset",
},
// For webpack v4
// {
// test: /\.(png|jpe?g|gif|svg|eot|ttf|woff|woff2)$/i,
// loader: "url-loader",
// options: {
// limit: 8192,
// },
// },
],
},
}; index.css
.class {
background: url(/assets/unresolved/img.png);
} webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: ["style-loader", "css-loader"],
},
],
},
resolve: {
alias: {
"/assets/unresolved/img.png": path.resolve(
__dirname,
"assets/real-path-to-img/img.png"
),
},
},
}; Interoperable CSS-only and CSS Module featuresThe 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}`;
Please take a moment to read our contributing guidelines if you haven't yet done so.