webpack-contrib
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 sass webpack --save-devor
yarn add -D sass-loader sass webpackor
pnpm add -D sass-loader sass webpack[!NOTE]
To enable CSS processing in your project, you need to install style-loader and css-loader via
npm i style-loader css-loader.
sass-loader requires you to install either Dart Sass, Node Sass on your own (more documentation can be found below) or Sass Embedded.
This allows you to control the versions of all your dependencies, and to choose which Sass implementation to use.
[!NOTE]
We highly recommend using Sass Embedded or Dart Sass.
[!WARNING]
Node Sass does not work with Yarn PnP and doesn't support @use rule.
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.
The style (new API, by default since 16 version) and outputStyle (old API) options in production mode
For production mode, the style (new API, by default since 16 version) and outputStyle (old API) options default to compressed unless otherwise specified in sassOptions.
Resolving import and use 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 enabling you to import your Sass modules from node_modules.
@import "bootstrap";Using ~ is deprecated and should be removed from your code, but we still support it for historical reasons.
Why can you remove it? The loader will first try to resolve @import as a relative path. If it cannot be resolved, then the loader will try to resolve @import inside node_modules.
Prepending module paths with a ~ tells webpack to search through node_modules.
@import "~bootstrap";It's important to prepend the path with only ~, 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 might be surprised by this first issue, as 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 two solutions to this problem:
- Add the missing url rewriting using the resolve-url-loader. Place it before
sass-loaderin the loader chain. - Library authors usually provide a variable to modify the asset path. bootstrap-sass for example has an
$icon-font-path.
Options
implementation
Type:
type implementation = object | string;Default: sass
The special implementation option determines which implementation of Sass to use.
By default, the loader resolves the implementation based on your dependencies.
Just add the desired implementation to your package.json (sass, sass-embedded, or node-sass package) and install dependencies.
Example where the sass-loader loader uses the sass (dart-sass) implementation:
package.json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"sass": "^1.22.10"
}
}Example where the sass-loader loader uses the node-sass implementation:
package.json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"node-sass": "^5.0.0"
}
}Example where the sass-loader loader uses the sass-embedded implementation:
package.json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"sass": "^1.22.10"
},
"optionalDependencies": {
"sass-embedded": "^1.70.0"
}
}[!NOTE]
Using
optionalDependenciesmeans thatsass-loadercan fallback tosasswhen running on an operating system not supported bysass-embedded
Be aware of the order that sass-loader will resolve the implementation:
sass-embeddedsassnode-sass
You can specify a specific implementation by using the implementation option, which accepts one of the above values.
object
For example, to always use Dart Sass, you'd pass:
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
// Prefer `dart-sass`, even if `sass-embedded` is available
implementation: require("sass"),
},
},
],
},
],
},
};string
For example, to use Dart Sass, you'd pass:
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
// Prefer `dart-sass`, even if `sass-embedded` is available
implementation: require.resolve("sass"),
},
},
],
},
],
},
};sassOptions
Type:
type sassOptions =
| import("sass").LegacyOptions<"async">
| ((
content: string | Buffer,
loaderContext: LoaderContext,
meta: any,
) => import("sass").LegacyOptions<"async">);Default: defaults values for Sass implementation
Options for Dart Sass or Node Sass implementation.
[!NOTE]
The
charsetoption istrueby default fordart-sass, we strongly discourage setting this tofalse, because webpack doesn't support files other thanutf-8.
[!NOTE]
The
syntax(new API, by default since 16 version)andindentedSyntax(old API) option isscssfor thescssextension,indentedfor thesassextension andcssfor thecss` extension.
[!NOTE]
Options such as
dataandfileare unavailable and will be ignored.
ℹ We strongly discourage changing the
sourceMap(new API, by default since 16 version),outFile(old API),sourceMapContents(old API),sourceMapEmbed(old API), andsourceMapRoot(old API) options becausesass-loadersets these automatically when thesourceMapoption istrue.
[!NOTE]
Access to the loader context inside the custom importer can be done using the
this.webpackLoaderContextproperty.
There is a slight difference between the options for sass (dart-sass) and node-sass.
Please consult their respective documentation before using them:
- Dart Sass documentation for all available
sassoptions. - Sass Embedded documentation for all available
sassoptions. - Node Sass documentation for all available
node-sassoptions.
object
Use an object for the Sass implementation setup.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
sassOptions: {
style: `compressed`,
loadPaths: ["absolute/path/a", "absolute/path/b"],
},
},
},
],
},
],
},
};function
Allows configuring the Sass implementation with different options based on the loader context.
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
sassOptions: (loaderContext) => {
// More information about available properties https://webpack.js.org/api/loaders/
const { resourcePath, rootContext } = loaderContext;
const relativePath = path.relative(rootContext, resourcePath);
if (relativePath === "styles/foo.scss") {
return {
loadPaths: ["absolute/path/c", "absolute/path/d"],
};
}
return {
loadPaths: ["absolute/path/a", "absolute/path/b"],
};
},
},
},
],
},
],
},
};sourceMap
Type:
type sourceMap = boolean;Default: depends on the compiler.devtool value
Enables/Disables generation of source maps.
By default generation of source maps depends on the devtool option.
All values enable source map generation except eval and false.
ℹ If
true, thesourceMap(new API, by default since 16 version),outFile(old API),sourceMapContents(old API),sourceMapEmbed(old API), andsourceMapRoot(old API) fromsassOptionswill be ignored.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
{
loader: "css-loader",
options: {
sourceMap: true,
},
},
{
loader: "sass-loader",
options: {
sourceMap: true,
},
},
],
},
],
},
};ℹ In some rare cases
node-sasscan output invalid source maps (it is anode-sassbug).In order to avoid this, you can try to update
node-sassto latest version, or you can try to set withinsassOptionstheoutputStyleoption tocompressed.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
sourceMap: true,
sassOptions: {
outputStyle: "compressed",
},
},
},
],
},
],
},
};additionalData
Type:
type additionalData =
| string
| ((content: string | Buffer, loaderContext: LoaderContext) => string);Default: undefined
Prepends Sass/SCSS code before the actual entry file.
In this case, the sass-loader will not override the data option but just prepend the entry's content.
This is especially useful when some of your Sass variables depend on the environment:
string
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
additionalData: "$env: " + process.env.NODE_ENV + ";",
},
},
],
},
],
},
};function
Sync
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
additionalData: (content, 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 "$value: 100px;" + content;
}
return "$value: 200px;" + content;
},
},
},
],
},
],
},
};Async
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
additionalData: async (content, loaderContext) => {
// More information about available properties https://webpack.js.org/api/loaders/
const { resourcePath, rootContext } = loaderContext;
const relativePath = path.relative(rootContext, resourcePath);
if (relativePath === "styles/foo.scss") {
return "$value: 100px;" + content;
}
return "$value: 200px;" + content;
},
},
},
],
},
],
},
};webpackImporter
Type:
type webpackImporter = boolean;Default: true
Enables/Disables the default webpack importer.
This can improve performance in some cases, though use it with caution because aliases and @import at-rules starting with ~ will not work.
You can pass your own importer to solve this (see importer docs).
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
webpackImporter: false,
},
},
],
},
],
},
};warnRuleAsWarning
Type:
type warnRuleAsWarning = boolean;Default: true
Treats the @warn rule as a webpack warning.
style.scss
$known-prefixes: webkit, moz, ms, o;
@mixin prefix($property, $value, $prefixes) {
@each $prefix in $prefixes {
@if not index($known-prefixes, $prefix) {
@warn "Unknown prefix #{$prefix}.";
}
-#{$prefix}-#{$property}: $value;
}
#{$property}: $value;
}
.tilt {
// Oops, we typo'd "webkit" as "wekbit"!
@include prefix(transform, rotate(15deg), wekbit ms);
}The presented code will throw a webpack warning instead logging.
To ignore unnecessary warnings you can use the ignoreWarnings option.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
warnRuleAsWarning: true,
},
},
],
},
],
},
};api
Type:
type api = "legacy" | "modern" | "modern-compiler";Default: "modern" for sass (dart-sass) and sass-embedded, or "legacy" for node-sass
Allows you to switch between the legacy and modern APIs. You can find more information here. The modern-compiler option enables the modern API with support for Shared Resources.
[!NOTE]
Using
modern-compilerandsass-embeddedtogether significantly improve performance and decrease built time. We strongly recommend their use. We will enable them by default in a future major release.
[!WARNING]
The sass options are different for the
legacyandmodernAPIs. Please look at docs how to migrate to the modern options.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
api: "modern-compiler",
sassOptions: {
// Your sass options
},
},
},
],
},
],
},
};How to enable @debug output
By default, the output of @debug messages are disabled.
Add the following to webpack.config.js to enable them:
module.exports = {
stats: {
loggingDebug: ["sass-loader"],
},
// ...
};Examples
Extracts CSS into separate files
For production builds it's recommended to extract the CSS from your bundle to be able to use parallel loading of CSS/JS resources later on.
There are four recommended ways to extract a stylesheet from a bundle:
1. mini-css-extract-plugin
webpack.config.js
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/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",
}),
],
};2. Asset Modules
webpack.config.js
module.exports = {
entry: [__dirname + "/src/scss/app.scss"],
module: {
rules: [
{
test: /\.js$/,
exclude: /node_modules/,
use: [],
},
{
test: /\.scss$/,
exclude: /node_modules/,
type: "asset/resource",
generator: {
filename: "bundle.css",
},
use: ["sass-loader"],
},
],
},
};3. extract-loader (simpler, but specialized on the css-loader's output)
4. file-loader (deprecated--should only be used in webpack v4)
webpack.config.js
module.exports = {
entry: [__dirname + "/src/scss/app.scss"],
module: {
rules: [
{
test: /\.js$/,
exclude: /node_modules/,
use: [],
},
{
test: /\.scss$/,
exclude: /node_modules/,
use: [
{
loader: "file-loader",
options: { outputPath: "css/", name: "[name].min.css" },
},
"sass-loader",
],
},
],
},
};(source: https://stackoverflow.com/a/60029923/2969615)
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: /\.s[ac]ss$/i,
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.