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css-loader
Advanced tools
The css-loader is a loader for webpack that interprets `@import` and `url()` like `import/require()` and will resolve them. It allows you to load CSS files with JavaScript and use CSS modules for local scope CSS.
Interpreting @import and url()
Allows importing CSS within JavaScript modules using @import and url() which will be resolved by webpack.
import './style.css';
CSS Modules
Enables the use of CSS Modules, where CSS classes are imported as an object of strings, allowing for local scope and composition of CSS classes.
import styles from './style.module.css'; console.log(styles.className);
Source Maps
Supports generation of source maps to enable debugging of CSS by linking the transformed code back to the original source.
module.exports = { module: { rules: [{ test: /\.css$/, use: ['style-loader', { loader: 'css-loader', options: { sourceMap: true } }] }] } };
Minification
In combination with other tools like CssMinimizerPlugin, it can be used to minify CSS for production builds.
module.exports = { optimization: { minimizer: ['...', new CssMinimizerPlugin()] } };
Import Loaders
Allows to configure how many loaders before css-loader should be applied to @imported resources.
module.exports = { module: { rules: [{ test: /\.css$/, use: ['style-loader', { loader: 'css-loader', options: { importLoaders: 1 } }, 'postcss-loader'] }] } };
Injects CSS into the DOM using multiple <style> tags. It is often used in conjunction with css-loader.
Loads and compiles Sass/SCSS files. It extends css-loader's functionality to work with Sass/SCSS syntax.
Processes Less files and compiles them to CSS. Similar to sass-loader, it's specific to Less preprocessor language.
Processes CSS with PostCSS, a tool for transforming CSS with JavaScript plugins. It can be used after css-loader to apply various transformations and optimizations.
Extracts CSS into separate files. It creates a CSS file per JS file which contains CSS. It is used for CSS splitting, and is more performant than style-loader for production builds.
npm install css-loader
var css = require("css!./file.css");
// => returns css code from file.css, resolves imports and url(...)
@import
and url(...)
are interpreted like require()
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 combatible to existing css files:
url(image.png)
=> require("./image.png")
url(~module/image.png)
=> require("module/image.png")
This webpack config can load css files, embed small png images as Data Urls and jpg images as files.
module.exports = {
module: {
loaders: [
{ test: /\.css$/, loader: "style-loader!css-loader" },
{ test: /\.png$/, loader: "url-loader?limit=100000&mimetype=image/png" },
{ test: /\.jpg$/, loader: "file-loader" }
]
}
};
For urls that start with a /
, the default behavior is to not translate them:
url(/image.png)
=> url(/image.png)
If a root
query parameter is set, however, it will be prepended to the url
and then translated:
With a config like:
loaders: [
{ test: /\.css$/, loader: "style-loader!css-loader?root=." },
...
]
The result is:
url(/image.png)
=> require("./image.png")
By default the css-loader minimizes the css if specified by the module system.
In some cases the structural minification is destructive to the css, so you can disable it with the disableStructuralMinification
query parameter. require("css-loader?disableStructuralMinification!./file.css")
FAQs
css loader module for webpack
The npm package css-loader receives a total of 18,417,627 weekly downloads. As such, css-loader popularity was classified as popular.
We found that css-loader demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 3 open source maintainers collaborating on the project.
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