sass-loader
Advanced tools
The sass-loader npm package is a loader for webpack that allows you to preprocess .scss or .sass files to standard CSS. It uses the Sass compiler to convert Sass code into CSS, and then webpack can bundle the resulting CSS into your final build.
Compiling Sass/SCSS to CSS
This webpack configuration snippet demonstrates how to set up sass-loader in conjunction with css-loader and style-loader to process .scss files.
module.exports = {
module: {
rules: [
{
test: /\.scss$/,
use: [
'style-loader',
'css-loader',
'sass-loader'
]
}
]
}
};Source Maps
This code enables source maps for easier debugging of Sass files. It configures sass-loader to generate source maps so that the browser dev tools can display the original Sass code instead of the compiled CSS.
module.exports = {
module: {
rules: [
{
test: /\.scss$/,
use: [
'style-loader',
{
loader: 'css-loader',
options: { sourceMap: true }
},
{
loader: 'sass-loader',
options: { sourceMap: true }
}
]
}
]
}
};Custom Functions
This example shows how to add custom functions to the Sass compilation process. The custom 'pow' function can be used within Sass files to compute powers.
const sass = require('sass');
module.exports = {
module: {
rules: [
{
test: /\.scss$/,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
sassOptions: {
functions: {
'pow($base, $exponent)': function(base, exponent) {
return new sass.types.Number(Math.pow(base.getValue(), exponent.getValue()));
}
}
}
}
}
]
}
]
}
};node-sass is a library that provides binding for Node.js to the Sass compiler. It allows you to natively compile .scss files to css at incredible speed. However, node-sass is deprecated in favor of Dart Sass.
postcss-loader is a tool that uses PostCSS to process CSS with JavaScript plugins. It can be used for tasks such as autoprefixing, linting, and more. While sass-loader focuses on compiling Sass, postcss-loader is more about post-processing CSS.
less-loader is similar to sass-loader but for Less, which is another preprocessor language that extends the capabilities of CSS. It's a loader for webpack that compiles Less to CSS.
stylus-loader enables webpack to compile Stylus files to CSS. Stylus is another CSS preprocessor scripting language, offering similar features to Sass/SCSS.
Loads a Sass/SCSS file and compiles it to CSS.
To begin, you'll need to install sass-loader:
npm install sass-loader sass webpack --save-dev
or
yarn add -D sass-loader sass webpack
or
pnpm add -D sass-loader sass webpack
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 Dart Sass.
Warning
Node Sass does not work with Yarn PnP feature and doesn't support @use rule.
Warning
Sass Embedded is experimental and in
beta, therefore some features may not work
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.
import at-rulesWebpack 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.
@import "bootstrap";
Using ~ is deprecated and can be removed from your code (we recommend it), 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 it 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";
url(...)Since Sass implementations don't provide url rewriting, all linked assets must be relative to the output.
css-loader, all urls must be relative to the entry-file (e.g. main.scss).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:
sass-loader in the loader chain.$icon-font-path.implementationType:
type implementation = object | string;
Default: sass
The special implementation option determines which implementation of Sass to use.
By default the loader resolve the implementation based on your dependencies.
Just add required implementation to package.json (sass or node-sass package) and install dependencies.
Example where the sass-loader loader uses the sass (dart-sass) implementation:
package.json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"sass": "^1.22.10"
}
}
Example where the sass-loader loader uses the node-sass implementation:
package.json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"node-sass": "^5.0.0"
}
}
Beware the situation when node-sass and sass were installed! By default the sass-loader prefers sass.
In order to avoid this situation you can use the implementation option.
The implementation options either accepts sass (Dart Sass) or node-sass as a module.
objectFor example, to use Dart Sass, you'd pass:
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
// Prefer `dart-sass`
implementation: require("sass"),
},
},
],
},
],
},
};
stringFor example, to use Dart Sass, you'd pass:
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
// Prefer `dart-sass`
implementation: require.resolve("sass"),
},
},
],
},
],
},
};
Note that when using sass (Dart Sass), synchronous compilation is twice as fast as asynchronous compilation by default, due to the overhead of asynchronous callbacks.
To avoid this overhead, you can use the fibers package to call asynchronous importers from the synchronous code path.
We automatically inject the fibers package (setup sassOptions.fiber) for Node.js less v16.0.0 if is possible (i.e. you need install the fibers package).
Warning
Fibers is not compatible with
Node.jsv16.0.0 or later. Unfortunately, v8 commit dacc2fee0f is a breaking change and workarounds are non-trivial. (see introduction to readme).
package.json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"sass": "^1.22.10",
"fibers": "^4.0.1"
}
}
You can disable automatically injecting the fibers package by passing a false value for the sassOptions.fiber option.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/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$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
implementation: require("sass"),
sassOptions: {
fiber: require("fibers"),
},
},
},
],
},
],
},
};
sassOptionsType:
type sassOptions =
| import("sass").LegacyOptions<"async">
| ((
content: string | Buffer,
loaderContext: LoaderContext,
meta: any
) => import("sass").LegacyOptions<"async">);
Default: defaults values for Sass implementation
Options for Dart Sass or Node Sass implementation.
Note
The
charsetoption hastruevalue by default fordart-sass, we strongly discourage change value tofalse, because webpack doesn't support files other thanutf-8.
Note
The
indentedSyntaxoption hastruevalue for thesassextension.
Note
Options such as
dataandfileare unavailable and will be ignored.
ℹ We strongly discourage change
outFile,sourceMapContents,sourceMapEmbed,sourceMapRootoptions becausesass-loaderautomatically sets these options when thesourceMapoption istrue.
Note
Access to the loader context inside the custom importer can be done using the
this.webpackLoaderContextproperty.
There is a slight difference between the sass (dart-sass) and node-sass options.
Please consult documentation before using them:
sass options.node-sass options.objectUse an object for the Sass implementation setup.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
sassOptions: {
indentWidth: 4,
includePaths: ["absolute/path/a", "absolute/path/b"],
},
},
},
],
},
],
},
};
functionAllows to setup the Sass implementation by setting different options based on the loader context.
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
sassOptions: (loaderContext) => {
// More information about available properties https://webpack.js.org/api/loaders/
const { resourcePath, rootContext } = loaderContext;
const relativePath = path.relative(rootContext, resourcePath);
if (relativePath === "styles/foo.scss") {
return {
includePaths: ["absolute/path/c", "absolute/path/d"],
};
}
return {
includePaths: ["absolute/path/a", "absolute/path/b"],
};
},
},
},
],
},
],
},
};
sourceMapType:
type sourceMap = boolean;
Default: depends on the compiler.devtool value
Enables/Disables generation of source maps.
By default generation of source maps depends on the devtool option.
All values enable source map generation except eval and false value.
ℹ If a
truethesourceMap,sourceMapRoot,sourceMapEmbed,sourceMapContentsandomitSourceMapUrlfromsassOptionswill be ignored.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/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$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
sourceMap: true,
sassOptions: {
outputStyle: "compressed",
},
},
},
],
},
],
},
};
additionalDataType:
type additionalData =
| string
| ((content: string | Buffer, loaderContext: LoaderContext) => string);
Default: undefined
Prepends Sass/SCSS code before the actual entry file.
In this case, the sass-loader will not override the data option but just prepend the entry's content.
This is especially useful when some of your Sass variables depend on the environment:
stringmodule.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
additionalData: "$env: " + process.env.NODE_ENV + ";",
},
},
],
},
],
},
};
functionmodule.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/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;
},
},
},
],
},
],
},
};
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 "$value: 200px;" + content;
},
},
},
],
},
],
},
};
webpackImporterType:
type webpackImporter = boolean;
Default: true
Enables/Disables the default Webpack importer.
This can improve performance in some cases. Use it with caution because aliases and @import at-rules starting with ~ will not work.
You can pass own importer to solve this (see importer docs).
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
webpackImporter: false,
},
},
],
},
],
},
};
warnRuleAsWarningType:
type warnRuleAsWarning = boolean;
Default: false
Treats the @warn rule as a webpack warning.
Note
It will be
trueby default in the next major release.
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}: $value;
}
.tilt {
// Oops, we typo'd "webkit" as "wekbit"!
@include prefix(transform, rotate(15deg), wekbit ms);
}
The presented code will throw webpack warning instead logging.
To ignore unnecessary warnings you can use the ignoreWarnings option.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
warnRuleAsWarning: true,
},
},
],
},
],
},
};
apiType:
type api = "legacy" | "modern";
Default: "legacy"
Allows you to switch between legacy and modern API. You can find more information here.
Warning
"modern" API is experimental, so some features may not work (known: built-in
importeris not working and files with errors is not watching on initial run), you can follow this here.
Warning
The sass options are different for
modernandoldAPIs. Please look at docs how to migrate on new options.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
api: "modern",
sassOptions: {
// Your sass options
},
},
},
],
},
],
},
};
@debug outputDefaults, the output of @debug messages is disabled.
To enable it, add to webpack.config.js following:
module.exports = {
stats: {
loggingDebug: ["sass-loader"],
},
// ...
};
For production builds it's recommended to extract the CSS from your bundle being able to use parallel loading of CSS/JS resources later on.
There are four possibilities to extract a style sheet from the bundle:
webpack.config.js
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/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",
}),
],
};
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"],
},
],
},
};
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)
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.
Please take a moment to read our contributing guidelines if you haven't yet done so.
FAQs
Sass loader for webpack
The npm package sass-loader receives a total of 2,550,588 weekly downloads. As such, sass-loader popularity was classified as popular.
We found that sass-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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