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
[!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: [
"style-loader",
"css-loader",
"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-loader
in the loader chain. - Library authors usually provide a variable to modify the asset path. bootstrap-sass for example has an
$icon-font-path
.
Options
implementation
Type:
type implementation = object | string;
Default: sass
The special implementation
option determines which implementation of Sass to use.
By default, the loader resolves the implementation based on your dependencies.
Just add the desired implementation to your package.json
(sass
, sass-embedded
, or node-sass
package) and install dependencies.
Example where the sass-loader
loader uses the sass
(dart-sass
) implementation:
package.json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"sass": "^1.22.10"
}
}
Example where the sass-loader
loader uses the node-sass
implementation:
package.json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"node-sass": "^5.0.0"
}
}
Example where the sass-loader
loader uses the sass-embedded
implementation:
package.json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"sass": "^1.22.10"
},
"optionalDependencies": {
"sass-embedded": "^1.70.0"
}
}
[!NOTE]
Using optionalDependencies
means that sass-loader
can fallback to sass
when running on an operating system not supported by sass-embedded
Be aware of the order that sass-loader
will resolve the implementation:
sass-embedded
sass
node-sass
You can specify a specific implementation by using the implementation
option, which accepts one of the above values.
object
For example, to always use Dart Sass, you'd pass:
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
implementation: require("sass"),
},
},
],
},
],
},
};
string
For example, to use Dart Sass, you'd pass:
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
implementation: require.resolve("sass"),
},
},
],
},
],
},
};
sassOptions
Type:
type sassOptions =
| import("sass").LegacyOptions<"async">
| ((
content: string | Buffer,
loaderContext: LoaderContext,
meta: any,
) => import("sass").LegacyOptions<"async">);
Default: defaults values for Sass implementation
Options for Dart Sass or Node Sass implementation.
[!NOTE]
The charset
option is true
by default for dart-sass
, we strongly discourage setting this to false
, because webpack doesn't support files other than utf-8
.
[!NOTE]
The syntax
(new API, by default since 16 version)and
indentedSyntax(old API) option is
scssfor the
scssextension,
indentedfor the
sassextension and
cssfor the
css` extension.
[!NOTE]
Options such as data
and file
are unavailable and will be ignored.
ℹ We strongly discourage changing the sourceMap
(new API, by default since 16 version), outFile
(old API), sourceMapContents
(old API), sourceMapEmbed
(old API), and sourceMapRoot
(old API) options because sass-loader
sets these automatically when the sourceMap
option is true
.
[!NOTE]
Access to the loader context inside the custom importer can be done using the this.webpackLoaderContext
property.
There is a slight difference between the options for sass
(dart-sass
) and node-sass
.
Please consult their respective documentation before using them:
object
Use an object for the Sass implementation setup.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/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$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
sassOptions: (loaderContext) => {
const { resourcePath, rootContext } = loaderContext;
const relativePath = path.relative(rootContext, resourcePath);
if (relativePath === "styles/foo.scss") {
return {
loadPaths: ["absolute/path/c", "absolute/path/d"],
};
}
return {
loadPaths: ["absolute/path/a", "absolute/path/b"],
};
},
},
},
],
},
],
},
};
sourceMap
Type:
type sourceMap = boolean;
Default: depends on the compiler.devtool
value
Enables/Disables generation of source maps.
By default generation of source maps depends on the devtool
option.
All values enable source map generation except eval
and false
.
ℹ If true
, the sourceMap
(new API, by default since 16 version), outFile
(old API), sourceMapContents
(old API), sourceMapEmbed
(old API), and sourceMapRoot
(old API) from sassOptions
will be ignored.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/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 a node-sass
bug).
In order to avoid this, you can try to update node-sass
to latest version, or you can try to set within sassOptions
the outputStyle
option to compressed
.
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) => {
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$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
additionalData: async (content, loaderContext) => {
const { resourcePath, rootContext } = loaderContext;
const relativePath = path.relative(rootContext, resourcePath);
if (relativePath === "styles/foo.scss") {
return "$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}: $value;
}
.tilt {
@include prefix(transform, rotate(15deg), wekbit ms);
}
The presented code will throw a webpack warning instead logging.
To ignore unnecessary warnings you can use the ignoreWarnings option.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/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-compiler
and sass-embedded
together 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 legacy
and modern
APIs. Please look at docs how to migrate to the modern options.
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
"style-loader",
"css-loader",
{
loader: "sass-loader",
options: {
api: "modern-compiler",
sassOptions: {
},
},
},
],
},
],
},
};
How to enable @debug
output
By default, the output of @debug
messages are disabled.
Add the following to webpack.config.js to enable them:
module.exports = {
stats: {
loggingDebug: ["sass-loader"],
},
};
Examples
For production builds it's recommended to extract the CSS from your bundle to be able to use parallel loading of CSS/JS resources later on.
There are four recommended ways to extract a stylesheet from a bundle:
webpack.config.js
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
process.env.NODE_ENV !== "production"
? "style-loader"
: MiniCssExtractPlugin.loader,
"css-loader",
"sass-loader",
],
},
],
},
plugins: [
new MiniCssExtractPlugin({
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"],
},
],
},
};
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",
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.
CONTRIBUTING
License
MIT