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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 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.
The outputStyle
(old API) and style
(new API) options in production
mode
For production
mode, the outputStyle
(old API) and style
(new API) options default to compressed
unless otherwise specified in sassOptions
.
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
.
@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";
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
$icon-font-path
.
Options
implementation
Type:
type implementation = object | string;
Default: sass
The special implementation
option determines which implementation of Sass to use.
By default the loader resolve the implementation based on your dependencies.
Just add required implementation to package.json
(sass
or node-sass
package) and install dependencies.
Example where the sass-loader
loader uses the sass
(dart-sass
) implementation:
package.json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"sass": "^1.22.10"
}
}
Example where the sass-loader
loader uses the node-sass
implementation:
package.json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"node-sass": "^5.0.0"
}
}
Beware the situation when node-sass
and sass
were installed! By default the sass-loader
prefers sass
.
In order to avoid this situation you can use the implementation
option.
The implementation
options either accepts sass
(Dart Sass
) or node-sass
as a module.
object
For example, to use Dart Sass, you'd pass:
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
// Prefer `dart-sass`
implementation: require("sass"),
},
},
],
},
],
},
};
string
For example, to use Dart Sass, you'd pass:
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
// Prefer `dart-sass`
implementation: require.resolve("sass"),
},
},
],
},
],
},
};
Note that when using sass
(Dart Sass
), synchronous compilation is twice as fast as asynchronous compilation by default, due to the overhead of asynchronous callbacks.
To avoid this overhead, you can use the fibers package to call asynchronous importers from the synchronous code path.
We automatically inject the fibers
package (setup sassOptions.fiber
) for Node.js
less v16.0.0 if is possible (i.e. you need install the fibers
package).
Warning
Fibers is not compatible with
Node.js
v16.0.0 or later. Unfortunately, v8 commit dacc2fee0f is a breaking change and workarounds are non-trivial. (see introduction to readme).
package.json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"sass": "^1.22.10",
"fibers": "^4.0.1"
}
}
You can disable automatically injecting the fibers
package by passing a false
value for the sassOptions.fiber
option.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/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$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
implementation: require("sass"),
sassOptions: {
fiber: require("fibers"),
},
},
},
],
},
],
},
};
sassOptions
Type:
type sassOptions =
| import("sass").LegacyOptions<"async">
| ((
content: string | Buffer,
loaderContext: LoaderContext,
meta: any
) => import("sass").LegacyOptions<"async">);
Default: defaults values for Sass implementation
Options for Dart Sass or Node Sass implementation.
Note
The
charset
option hastrue
value by default fordart-sass
, we strongly discourage change value tofalse
, because webpack doesn't support files other thanutf-8
.
Note
The
indentedSyntax
option hastrue
value for thesass
extension.
Note
Options such as
data
andfile
are unavailable and will be ignored.
ℹ We strongly discourage change
outFile
,sourceMapContents
,sourceMapEmbed
,sourceMapRoot
options becausesass-loader
automatically sets these options when thesourceMap
option istrue
.
Note
Access to the loader context inside the custom importer can be done using the
this.webpackLoaderContext
property.
There is a slight difference between the sass
(dart-sass
) and node-sass
options.
Please consult documentation before using them:
- Dart Sass documentation for all available
sass
options. - Node Sass documentation for all available
node-sass
options.
object
Use an object for the Sass implementation setup.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
sassOptions: {
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$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
sassOptions: (loaderContext) => {
// More information about available properties https://webpack.js.org/api/loaders/
const { resourcePath, rootContext } = loaderContext;
const relativePath = path.relative(rootContext, resourcePath);
if (relativePath === "styles/foo.scss") {
return {
includePaths: ["absolute/path/c", "absolute/path/d"],
};
}
return {
includePaths: ["absolute/path/a", "absolute/path/b"],
};
},
},
},
],
},
],
},
};
sourceMap
Type:
type sourceMap = boolean;
Default: depends on the compiler.devtool
value
Enables/Disables generation of source maps.
By default generation of source maps depends on the devtool
option.
All values enable source map generation except eval
and false
value.
ℹ If a
true
thesourceMap
,sourceMapRoot
,sourceMapEmbed
,sourceMapContents
andomitSourceMapUrl
fromsassOptions
will be ignored.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
{
loader: "css-loader",
options: {
sourceMap: true,
},
},
{
loader: "sass-loader",
options: {
sourceMap: true,
},
},
],
},
],
},
};
ℹ In some rare cases
node-sass
can output invalid source maps (it is anode-sass
bug).
In order to avoid this, you can try to update
node-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$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
sourceMap: true,
sassOptions: {
outputStyle: "compressed",
},
},
},
],
},
],
},
};
additionalData
Type:
type additionalData =
| string
| ((content: string | Buffer, loaderContext: LoaderContext) => string);
Default: undefined
Prepends Sass
/SCSS
code before the actual entry file.
In this case, the sass-loader
will not override the data
option but just prepend the entry's content.
This is especially useful when some of your Sass variables depend on the environment:
string
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/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 "$value: 200px;" + content;
},
},
},
],
},
],
},
};
webpackImporter
Type:
type webpackImporter = boolean;
Default: true
Enables/Disables the default Webpack importer.
This can improve performance in some cases. Use it with caution because aliases and @import
at-rules starting with ~
will not work.
You can pass own importer
to solve this (see importer docs
).
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
webpackImporter: false,
},
},
],
},
],
},
};
warnRuleAsWarning
Type:
type warnRuleAsWarning = boolean;
Default: false
Treats the @warn
rule as a webpack warning.
Note
It will be
true
by 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,
},
},
],
},
],
},
};
api
Type:
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
importer
is not working and files with errors is not watching on initial run), you can follow this here.
Warning
The sass options are different for
modern
andold
APIs. Please look at docs how to migrate on new options.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
api: "modern",
sassOptions: {
// Your sass options
},
},
},
],
},
],
},
};
How to enable @debug
output
Defaults, the output of @debug
messages is disabled.
To enable it, add to webpack.config.js following:
module.exports = {
stats: {
loggingDebug: ["sass-loader"],
},
// ...
};
Examples
Extracts CSS into separate files
For production builds it's recommended to extract the CSS from your bundle being able to use parallel loading of CSS/JS resources later on.
There are four possibilities to extract a style sheet from the bundle:
1. mini-css-extract-plugin
webpack.config.js
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/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.