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README.md
sass-loader
Loads a Sass/SCSS file and compiles it to CSS.
Getting Started
To begin, you'll need to install sass-loader
:
npm install sass-loader node-sass webpack --save-dev
sass-loader
requires you to install either Node Sass or Dart Sass on your own (more documentation can be found below).
This allows you to control the versions of all your dependencies, and to choose which Sass implementation to use.
Chain the sass-loader
with the css-loader and the style-loader to immediately apply all styles to the DOM or the mini-css-extract-plugin to extract it into a separate file.
Then add the loader to your Webpack configuration. For example:
app.js
import './style.scss';
style.scss
$body-color: red;
body {
color: $body-color;
}
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
// Creates `style` nodes from JS strings
'style-loader',
// Translates CSS into CommonJS
'css-loader',
// Compiles Sass to CSS
'sass-loader',
],
},
],
},
};
Finally run webpack
via your preferred method.
Resolving import
at-rules
Webpack provides an advanced mechanism to resolve files.
The sass-loader
uses Sass's custom importer feature to pass all queries to the Webpack resolving engine. Thus you can import your Sass modules from node_modules
. Just prepend them with a ~
to tell Webpack that this is not a relative import:
@import '~bootstrap';
It's important to only prepend it with ~
, because ~/
resolves to the home directory.
Webpack needs to distinguish between bootstrap
and ~bootstrap
because CSS and Sass files have no special syntax for importing relative files.
Writing @import "style.scss"
is the same as @import "./style.scss";
Problems with url(...)
Since Sass implementations don't provide url rewriting, all linked assets must be relative to the output.
- If you pass the generated CSS on to the
css-loader
, all urls must be relative to the entry-file (e.g.main.scss
). - If you're just generating CSS without passing it to the
css-loader
, it must be relative to your web root.
You will be disrupted by this first issue. It is natural to expect relative references to be resolved against the .sass
/.scss
file in which they are specified (like in regular .css
files).
Thankfully there are a two solutions to this problem:
- Add the missing url rewriting using the resolve-url-loader. Place it before
sass-loader
in the loader chain. - Library authors usually provide a variable to modify the asset path. bootstrap-sass for example has an
$icon-font-path
.
Options
implementation
The special implementation
option determines which implementation of Sass to use.
By default the loader resolve the implementation based on your dependencies.
Just add required implementation to package.json
(node-sass
or sass
package) and install dependencies.
Example where the sass-loader
loader uses the sass
(dart-sass
) implementation:
package.json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"sass": "^1.22.10"
}
}
Example where the sass-loader
loader uses the node-sass
implementation:
package.json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"node-sass": "^4.0.0"
}
}
Beware the situation when node-sass
and sass
were installed! By default the sass-loader
prefers node-sass
. In order to avoid this situation you can use the implementation
option.
The implementation
options either accepts node-sass
or sass
(Dart Sass
) as a module.
For example, to use Dart Sass, you'd pass:
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
// Prefer `dart-sass`
implementation: require('sass'),
},
},
],
},
],
},
};
Note that when using sass
(Dart Sass
), synchronous compilation is twice as fast as asynchronous compilation by default, due to the overhead of asynchronous callbacks.
To avoid this overhead, you can use the fibers package to call asynchronous importers from the synchronous code path.
We automatically inject the fibers
package (setup sassOptions.fiber
) if is possible (i.e. you need install the fibers
package).
package.json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"sass": "^1.22.10",
"fibers": "^4.0.1"
}
}
You can disable automatically injecting the fibers
package by passing a false
value for the sassOptions.fiber
option.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
implementation: require('sass'),
sassOptions: {
fiber: false,
},
},
},
],
},
],
},
};
You can also pass the fiber
value using this code:
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
implementation: require('sass'),
sassOptions: {
fiber: require('fibers'),
},
},
},
],
},
],
},
};
sassOptions
Type: Object|Function
Options for Node Sass or Dart Sass implementation.
ℹ️ The
indentedSyntax
option hastrue
value for thesass
extension.
ℹ️ Options such as
file
andoutFile
are unavailable.
ℹ We recommend not to use the
sourceMapContents
,sourceMapEmbed
,sourceMapRoot
options becausesass-loader
automatically sets these options.
There is a slight difference between the node-sass
and sass
(Dart Sass
) options.
Please consult documentation before using them:
- Node Sass documentation for all available
node-sass
options. - Dart Sass documentation for all available
sass
options.
Object
Use and object for the Sass implementation setup.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
sassOptions: {
indentWidth: 4,
includePaths: ['absolute/path/a', 'absolute/path/b'],
},
},
},
],
},
],
},
};
Function
Allows to setup the Sass implementation by setting different options based on the loader context.
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
sassOptions: (loaderContext) => {
// More information about available properties https://webpack.js.org/api/loaders/
const { resourcePath, rootContext } = loaderContext;
const relativePath = path.relative(rootContext, resourcePath);
if (relativePath === 'styles/foo.scss') {
return {
includePaths: ['absolute/path/c', 'absolute/path/d'],
};
}
return {
includePaths: ['absolute/path/a', 'absolute/path/b'],
};
},
},
},
],
},
],
},
};
prependData
Type: String|Function
Default: undefined
Prepends Sass
/SCSS
code before the actual entry file.
In this case, the sass-loader
will not override the data
option but just append the entry's content.
This is especially useful when some of your Sass variables depend on the environment:
ℹ Since you're injecting code, this will break the source mappings in your entry file. Often there's a simpler solution than this, like multiple Sass entry files.
String
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
prependData: '$env: ' + process.env.NODE_ENV + ';',
},
},
],
},
],
},
};
Function
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
prependData: (loaderContext) => {
// More information about available properties https://webpack.js.org/api/loaders/
const { resourcePath, rootContext } = loaderContext;
const relativePath = path.relative(rootContext, resourcePath);
if (relativePath === 'styles/foo.scss') {
return '$value: 100px;';
}
return '$value: 200px;';
},
},
},
],
},
],
},
};
sourceMap
Type: Boolean
Default: depends on the compiler.devtool
value
Enables/Disables generation of source maps.
By default generation of source maps depends on the devtool
option. All values enable source map generation except eval
and false
value.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
{
loader: 'css-loader',
options: {
sourceMap: true,
},
},
{
loader: 'sass-loader',
options: {
sourceMap: true,
},
},
],
},
],
},
};
ℹ In some rare cases
node-sass
can output invalid source maps (it is anode-sass
bug). In order to avoid this, you can try to updatenode-sass
to latest version or you can try to set withinsassOptions
theoutputStyle
option tocompressed
.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
sourceMap: true,
sassOptions: {
outputStyle: 'compressed',
},
},
],
},
],
},
};
webpackImporter
Type: Boolean
Default: true
Enables/Disables the default Webpack importer.
This can improve performance in some cases. Use it with caution because aliases and @import
at-rules starting with ~
will not work. You can pass own importer
to solve this (see importer docs
).
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
webpackImporter: false,
},
},
],
},
],
},
};
Examples
Extracts CSS into separate files
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.
There are two possibilities to extract a style sheet from the bundle:
- mini-css-extract-plugin (use this, when using webpack 4 configuration. Works in all use-cases)
- extract-loader (simpler, but specialized on the css-loader's output)
webpack.config.js
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
// fallback to style-loader in development
process.env.NODE_ENV !== 'production'
? 'style-loader'
: MiniCssExtractPlugin.loader,
'css-loader',
'sass-loader',
],
},
],
},
plugins: [
new MiniCssExtractPlugin({
// Options similar to the same options in webpackOptions.output
// both options are optional
filename: '[name].css',
chunkFilename: '[id].css',
}),
],
};
Source maps
Enables/Disables generation of source maps.
To enable CSS source maps, you'll need to pass the sourceMap
option to the sass-loader
and the css-loader.
webpack.config.js
module.exports = {
devtool: 'source-map', // any "source-map"-like devtool is possible
module: {
rules: [
{
test: /\.scss$/,
use: [
'style-loader',
{
loader: 'css-loader',
options: {
sourceMap: true,
},
},
{
loader: 'sass-loader',
options: {
sourceMap: true,
},
},
],
},
],
},
};
If you want to edit the original Sass files inside Chrome, there's a good blog post. Checkout test/sourceMap for a running example.
Contributing
Please take a moment to read our contributing guidelines if you haven't yet done so.