npm install --save-dev css-loader
The css-loader
interprets @import
and url()
like requires
.
Use the loader either via your webpack config, CLI or inline.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/,
use: [ 'style-loader', 'css-loader' ]
}
]
}
}
In your application
import css from 'file.css';
webpack --module-bind 'css=style-loader!css-loader'
In your application
import css from 'file.css';
In your application
import css from 'style-loader!css-loader!./file.css';
@import
and url()
are interpreted like import
and will be resolved by the css-loader.
Good loaders for requiring your assets are the file-loader
and the url-loader which you should specify in your config (see below).
To be compatible with existing css files (if not in CSS Module mode):
url(image.png)
=>require('./image.png')
url(~module/image.png)
=>require('module/image.png')
Name | Default | Description |
---|---|---|
root |
/ |
Path to resolve URLs, URLs starting with / will not be translated |
modules |
false |
Enable/Disable CSS Modules |
import |
true |
Enable/Disable @import handling |
url |
true |
Enable/Disable url() handling |
minimize |
false |
Enable/Disable minification |
sourceMap |
false |
Enable/Disable Sourcemaps |
camelCase |
false |
Export Classnames in CamelCase |
importLoaders |
0 |
Number of loaders applied before CSS loader |
alias |
{} |
Create aliases to import certain modules more easily |
The following webpack config can load CSS files, embed small PNG/JPG/GIF/SVG images as well as fonts as Data URLs and copy larger files to the output directory.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.css$/,
use: [ 'style-loader', 'css-loader' ]
},
{
test: /\.(png|jpg|gif|svg|eot|ttf|woff|woff2)$/,
loader: 'url-loader',
options: {
limit: 10000
}
}
]
}
};
For URLs that start with a /
, the default behavior is to not translate them:
url(/image.png)
=>url(/image.png)
If a root
query parameter is set, however, it will be prepended to the URL
and then translated:
webpack.config.js
rules: [
{
test: /\.css$/,
use: [
'style-loader',
{
loader: 'css-loader',
options: { root: '.' }
}
]
}
]
url(/image.png)
=>require('./image.png')
Using 'Root-relative' urls is not recommended. You should only use it for legacy CSS files.
By default CSS exports all class names into a global selector scope. 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. :global(.className)
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 choosen unique identifiers are exported by the module.
app.css
:local(.className) { background: red; }
:local .className { color: green; }
:local(.className .subClass) { color: green; }
:local .className .subClass :global(.global-class-name) { color: blue; }
app.bundle.css
._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; }
Note: Identifiers are exported
exports.locals = {
className: '_23_aKvs-b8bW2Vg3fwHozO',
subClass: '_13LGdX8RMStbBE9w-t0gZ1'
}
CamelCase is recommended for local selectors. They are easier to use in the within the imported JS module.
url()
URLs in block scoped (:local .abc
) rules behave like requests in modules:
./file.png
instead offile.png
module/file.png
instead of~module/file.png
You can use :local(#someId)
, but this is not recommended. Use classes instead of ids.
You can configure the generated ident with the localIdentName
query parameter (default [hash:base64]
).
webpack.config.js
{
test: /\.css$/,
use: [
{
loader: 'css-loader',
options: {
modules: true,
localIdentName: '[path][name]__[local]--[hash:base64:5]'
}
}
]
}
You can also specify the absolute path to your custom getLocalIdent
function to generate classname based on a different schema. Note that this requires webpack >= v2.x.
since to be able to pass function in. For example:
{
test: /\.css$/,
use: [
{
loader: 'css-loader',
options: {
modules: true,
localIdentName: '[path][name]__[local]--[hash:base64:5]',
getLocalIdent: (context, localIdentName, localName, options) => {
return 'whatever_random_class_name'
}
}
}
]
}
Note: For prerendering with extract-text-webpack-plugin you should use css-loader/locals
instead of style-loader!css-loader
in the prerendering bundle. It doesn't embed CSS but only exports the identifier mappings.
The query parameter modules
enables the CSS Modules spec.
This enables local scoped CSS by default. (You can switch it off with :global(...)
or :global
for selectors and/or rules.)
When declaring a local class name you can compose a local class from another local class name.
: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 class names:
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 class name from another module:
:local(.continueButton) {
composes: button from 'library/button.css';
background: red;
}
:local(.nameEdit) {
composes: edit highlight from './edit.css';
background: red;
}
To import from multiple modules use multiple composes:
rules.
:local(.className) {
composes: edit hightlight from './edit.css';
composes: button from 'module/button.css';
composes: classFromThisModule;
background: red;
}
To include Sourcemaps set the sourceMap
query param.
I. e. the extract-text-webpack-plugin can handle them.
They are not enabled by default because they expose a runtime overhead and increase in bundle size (JS SourceMap do not). In addition to that relative paths are buggy and you need to use an absolute public path which include the server URL.
webpack.config.js
{
test: /\.css$/,
use: [
{
loader: 'css-loader',
options: {
sourceMap: true
}
}
]
}
You can also use the css-loader results directly as string, such as in Angular's component style.
webpack.config.js
{
test: /\.css$/,
use: [
{
loaders: ['to-string-loader', 'css-loader']
}
]
}
or
const cssText = require('./test.css').toString();
console.log(cssText);
If there are SourceMaps, they will also be included in the result string.
The query parameter importLoaders
allow to configure which loaders should be applied to @import
ed resources.
importLoaders
: That many loaders after the css-loader are used to import resources.
webpack.config.js
{
test: /\.css$/,
use: [
{
loader: 'css-loader',
options: {
importLoaders: 1
}
},
'postcss-loader'
]
}
This may change in the future, when the module system (i. e. webpack) supports loader matching by origin.
By default the css-loader minimizes the css if specified by the module system.
In some cases the minification is destructive to the css, so you can provide some options to it. cssnano is used for minification and you find a list of options here.
You can also disable or enforce minification with the minimize
query parameter.
webpack.config.js
{
test: /\.css$/,
use: [
{
loader: 'css-loader',
options: {
minimize: true || {/* CSSNano Options */}
}
}
]
}
By default, the exported JSON keys mirror the class names. If you want to camelize class names (useful in JS), pass the query parameter camelCase
to css-loader.
Option | Description |
---|---|
true |
Class names will be camelized |
'dashes' |
Only dashes in class names will be camelized |
'only' |
Introduced in 0.27.1 . Class names will be camelized, the original class name will be removed from the locals |
'dashesOnly' |
Introduced in 0.27.1 . Dashes in class names will be camelized, the original class name will be removed from the locals |
webpack.config.js
{
test: /\.css$/,
use: [
{
loader: 'css-loader',
options: {
camelCase: true
}
}
]
}
.class-name {}
import { className } from 'file.css';
Rewrite your urls with alias, this is useful when it's hard to change url paths of your input files, for example, when you're using some css / sass files in another package (bootstrap, ratchet, font-awesome, etc.).
css-loader's alias
follows the same syntax as webpack's resolve.alias
, you can see the details at: https://webpack.js.org/configuration/resolve/#resolve-alias
webpack.config.js
{
test: /\.scss$/,
use: [{
loader: "style-loader"
}, {
loader: "css-loader",
options: {
alias: {
"../fonts/bootstrap": "bootstrap-sass/assets/fonts/bootstrap"
}
}
}, {
loader: "sass-loader",
options: {
includePaths: [
path.resolve("./node_modules/bootstrap-sass/assets/stylesheets")
]
}
}]
}
@charset "UTF-8";
@import "bootstrap";
Check out this working bootstrap example.
Juho Vepsäläinen |
Joshua Wiens |
Kees Kluskens |
Sean Larkin |