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$/i,
use: ["style-loader", "css-loader"],
},
],
},
};
Good loaders for requiring your assets are the file-loader and the url-loader which you should specify in your config (see below).
And run webpack
via your preferred method.
You can also use the css-loader results directly as a string, such as in Angular's component style.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/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$/i,
use: [
"handlebars-loader", // handlebars loader expects raw resource string
"extract-loader",
"css-loader",
],
},
],
},
};
Name | Type | Default | Description |
---|---|---|---|
url |
{Boolean|Function} |
true |
Enables/Disables url /image-set functions handling |
import |
{Boolean|Function} |
true |
Enables/Disables @import at-rules handling |
modules |
{Boolean|String|Object} |
{auto: true} |
Enables/Disables CSS Modules and their configuration |
sourceMap |
{Boolean} |
compiler.devtool |
Enables/Disables generation of source maps |
importLoaders |
{Number} |
0 |
Enables/Disables or setups number of loaders applied before CSS loader |
esModule |
{Boolean} |
true |
Use ES modules syntax |
Type: Boolean|Function
Default: true
Enables/Disables url
/image-set
functions handling.
Control url()
resolving. Absolute URLs are not resolving.
Examples resolutions:
url(image.png) => require('./image.png')
url('image.png') => require('./image.png')
url(./image.png) => require('./image.png')
url('./image.png') => require('./image.png')
url('http://dontwritehorriblecode.com/2112.png') => require('http://dontwritehorriblecode.com/2112.png')
image-set(url('image2x.png') 1x, url('image1x.png') 2x) => require('./image1x.png') and require('./image2x.png')
To import assets from a node_modules
path (include resolve.modules
) and for alias
, prefix it with a ~
:
url(~module/image.png) => require('module/image.png')
url('~module/image.png') => require('module/image.png')
url(~aliasDirectory/image.png) => require('otherDirectory/image.png')
Enable/disable url()
resolving.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
url: true,
},
},
],
},
};
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$/i,
loader: "css-loader",
options: {
url: (url, resourcePath) => {
// resourcePath - path to css file
// Don't handle `img.png` urls
if (url.includes("img.png")) {
return false;
}
return true;
},
},
},
],
},
};
Type: Boolean|Function
Default: true
Enables/Disables @import
at-rules handling.
Control @import
resolving. Absolute urls in @import
will be moved in runtime code.
Examples resolutions:
@import 'style.css' => require('./style.css')
@import url(style.css) => require('./style.css')
@import url('style.css') => require('./style.css')
@import './style.css' => require('./style.css')
@import url(./style.css) => require('./style.css')
@import url('./style.css') => require('./style.css')
@import url('http://dontwritehorriblecode.com/style.css') => @import url('http://dontwritehorriblecode.com/style.css') in runtime
To import styles from a node_modules
path (include resolve.modules
) and for alias
, prefix it with a ~
:
@import url(~module/style.css) => require('module/style.css')
@import url('~module/style.css') => require('module/style.css')
@import url(~aliasDirectory/style.css) => require('otherDirectory/style.css')
Enable/disable @import
resolving.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
import: true,
},
},
],
},
};
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$/i,
loader: "css-loader",
options: {
import: (url, media, resourcePath) => {
// resourcePath - path to css file
// Don't handle `style.css` import
if (url.includes("style.css")) {
return false;
}
return true;
},
},
},
],
},
};
Type: Boolean|String|Object
Default: based on filename, true
for all files matching /\.module\.\w+$/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,
},
},
],
},
};
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.
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;
}
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;
}
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;
}
}
Enable CSS Modules features.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: true,
},
},
],
},
};
Enable CSS Modules features and setup mode
.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
// Using `local` value has same effect like using `modules: true`
modules: "global",
},
},
],
},
};
Enable CSS Modules features and setup options for them.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
compileType: "module",
mode: "local",
auto: true,
exportGlobals: true,
localIdentName: "[path][name]__[local]--[hash:base64:5]",
localIdentContext: path.resolve(__dirname, "src"),
localIdentHashPrefix: "my-custom-hash",
namedExport: true,
exportLocalsConvention: "camelCase",
exportOnlyLocals: false,
},
},
},
],
},
};
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$/i,
loader: "css-loader",
options: {
modules: {
compileType: "icss",
},
},
},
],
},
};
Type: Boolean|RegExp|Function
Default: 'true'
Allows auto enable CSS modules based on filename.
Possible values:
true
- enable css modules for all files for which/\.module\.\w+$/i.test(filename)
return truefalse
- disable css modules
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
auto: true,
},
},
},
],
},
};
Enable css modules for files based on the filename satisfying your regex check.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
auto: /\.custom-module\.\w+$/i,
},
},
},
],
},
};
Enable css modules for files based on the filename satisfying your filter function check.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
auto: (resourcePath) => resourcePath.endsWith(".custom-module.css"),
},
},
},
],
},
};
Type: String|Function
Default: 'local'
Setup mode
option. You can omit the value when you want local
mode.
Possible values - local
, global
, and pure
.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
mode: "global",
},
},
},
],
},
};
Allows set different values for the mode
option based on a filename
Possible return values - local
, global
, and pure
.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/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";
},
},
},
},
],
},
};
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$/i,
loader: "css-loader",
options: {
modules: {
localIdentName: "[path][name]__[local]--[hash:base64:5]",
},
},
},
],
},
};
Type: String
Default: compiler.context
Allows to redefine basic loader context for local ident name.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
localIdentContext: path.resolve(__dirname, "src"),
},
},
},
],
},
};
Type: String
Default: undefined
Allows to add custom hash to generate more unique classes.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
localIdentHashPrefix: "hash",
},
},
},
],
},
};
Type: String|RegExp
Default: undefined
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
localIdentRegExp: /page-(.*)\.css/i,
},
},
},
],
},
};
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$/i,
loader: "css-loader",
options: {
modules: {
getLocalIdent: (context, localIdentName, localName, options) => {
return "whatever_random_class_name";
},
},
},
},
],
},
};
Type: Boolean
Default: false
Enables/disables ES modules named export for locals.
⚠ Names of locals are converted to camelcase, i.e. the
exportLocalsConvention
option hascamelCaseOnly
value by default.
⚠ It is not allowed to use JavaScript reserved words in css class names.
styles.css
.foo-baz {
color: red;
}
.bar {
color: blue;
}
index.js
import { fooBaz, bar } from "./styles.css";
console.log(fooBaz, bar);
You can enable a ES module named export using:
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
esModule: true,
modules: {
namedExport: true,
},
},
},
],
},
};
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$/i,
loader: "css-loader",
options: {
modules: {
exportGlobals: true,
},
},
},
],
},
};
Type: String
Default: based on the modules.namedExport
option value, if true
- camelCaseOnly
, otherwise asIs
Style of exported class names.
By default, the exported JSON keys mirror the class names (i.e asIs
value).
⚠ Only
camelCaseOnly
value allowed if you set thenamedExport
value totrue
.
Name | Type | Description |
---|---|---|
'asIs' |
{String} |
Class names will be exported as is. |
'camelCase' |
{String} |
Class names will be camelized, the original class name will not to be removed from the locals |
'camelCaseOnly' |
{String} |
Class names will be camelized, the original class name will be removed from the locals |
'dashes' |
{String} |
Only dashes in class names will be camelized |
'dashesOnly' |
{String} |
Dashes in class names will be camelized, the original class name will be removed from the locals |
file.css
.class-name {
}
file.js
import { className } from "file.css";
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
modules: {
exportLocalsConvention: "camelCase",
},
},
},
],
},
};
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$/i,
loader: "css-loader",
options: {
modules: {
exportOnlyLocals: true,
},
},
},
],
},
};
Type: Boolean
Default: depends on the compiler.devtool
value
By default generation of source maps depends on the devtool
option. All values enable source map generation except eval
and false
value.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
sourceMap: true,
},
},
],
},
};
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$/i,
use: [
"style-loader",
{
loader: "css-loader",
options: {
importLoaders: 2,
// 0 => no loaders (default);
// 1 => postcss-loader;
// 2 => postcss-loader, sass-loader
},
},
"postcss-loader",
"sass-loader",
],
},
],
},
};
This may change in the future when the module system (i. e. webpack) supports loader matching by origin.
Type: Boolean
Default: true
By default, css-loader
generates JS modules that use the ES modules syntax.
There are some cases in which using ES modules is beneficial, like in the case of module concatenation and tree shaking.
You can enable a CommonJS modules syntax using:
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "css-loader",
options: {
esModule: false,
},
},
],
},
};
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,
},
},
],
},
};
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,
// 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,
},
},
],
},
};
index.css
.class {
background: url(/assets/unresolved/img.png);
}
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: ["style-loader", "css-loader"],
},
],
},
resolve: {
alias: {
"/assets/unresolved/img.png": path.resolve(
__dirname,
"assets/real-path-to-img/img.png"
),
},
},
};
The following setup is an example of allowing Interoperable CSS
features only (such as :import
and :export
) without using further CSS Module
functionality by setting compileType
option for all files that do not match *.module.scss
naming convention. This is for reference as having ICSS
features applied to all files was default css-loader
behavior before v4.
Meanwhile all files matching *.module.scss
are treated as CSS Modules
in this example.
An example case is assumed where a project requires canvas drawing variables to be synchronized with CSS - canvas drawing uses the same color (set by color name in JavaScript) as HTML background (set by class name in CSS).
webpack.config.js
module.exports = {
module: {
rules: [
// ...
// --------
// SCSS ALL EXCEPT MODULES
{
test: /\.scss$/,
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}`;
Please take a moment to read our contributing guidelines if you haven't yet done so.