[![npm][npm]][npm-url] [![node][node]][node-url] [![tests][tests]][tests-url] [![coverage][cover]][cover-url] [![chat][chat]][chat-url] [![size][size]][size-url] # sass-loader Loads a Sass/SCSS file and compiles it to CSS. ## Getting Started To begin, you'll need to install `sass-loader`: ```console npm install sass-loader sass webpack --save-dev ``` or ```console yarn add -D sass-loader sass webpack ``` or ```console pnpm add -D sass-loader sass webpack ``` `sass-loader` requires you to install either [Dart Sass](https://github.com/sass/dart-sass), [Node Sass](https://github.com/sass/node-sass) on your own (more documentation can be found below) or [Sass Embedded](https://github.com/sass/embedded-host-node). 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](https://github.com/sass/dart-sass). > **Warning** > > [Node Sass](https://github.com/sass/node-sass) does not work with [Yarn PnP](https://classic.yarnpkg.com/en/docs/pnp/) feature and doesn't support [@use rule](https://sass-lang.com/documentation/at-rules/use). > **Warning** > > [Sass Embedded](https://github.com/sass/embedded-host-node) is experimental and in `beta`, therefore some features may not work Chain the `sass-loader` with the [css-loader](https://github.com/webpack-contrib/css-loader) and the [style-loader](https://github.com/webpack-contrib/style-loader) to immediately apply all styles to the DOM or the [mini-css-extract-plugin](https://github.com/webpack-contrib/mini-css-extract-plugin) to extract it into a separate file. Then add the loader to your Webpack configuration. For example: **app.js** ```js import "./style.scss"; ``` **style.scss** ```scss $body-color: red; body { color: $body-color; } ``` **webpack.config.js** ```js module.exports = { module: { rules: [ { test: /\.s[ac]ss$/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](https://webpack.js.org/concepts/module-resolution/). 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`. ```scss @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`](https://webpack.js.org/configuration/resolve/#resolvemodules). Prepending module paths with a `~` tells webpack to search through [`node_modules`](https://webpack.js.org/configuration/resolve/#resolvemodules). ```scss @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](https://github.com/sass/libsass/issues/532), 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](https://github.com/bholloway/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](https://github.com/twbs/bootstrap-sass) for example has an `$icon-font-path`. ## Options - **[`implementation`](#implementation)** - **[`sassOptions`](#sassoptions)** - **[`sourceMap`](#sourcemap)** - **[`additionalData`](#additionaldata)** - **[`webpackImporter`](#webpackimporter)** - **[`warnRuleAsWarning`](#warnruleaswarning)** ### `implementation` Type: ```ts type implementation = object | string; ``` Default: `sass` The special `implementation` option determines which implementation of Sass to use. By default the loader resolve the implementation based on your dependencies. Just add required implementation to `package.json` (`sass` or `node-sass` package) and install dependencies. Example where the `sass-loader` loader uses the `sass` (`dart-sass`) implementation: **package.json** ```json { "devDependencies": { "sass-loader": "^7.2.0", "sass": "^1.22.10" } } ``` Example where the `sass-loader` loader uses the `node-sass` implementation: **package.json** ```json { "devDependencies": { "sass-loader": "^7.2.0", "node-sass": "^5.0.0" } } ``` Beware the situation when `node-sass` and `sass` were installed! By default the `sass-loader` prefers `sass`. In order to avoid this situation you can use the `implementation` option. The `implementation` options either accepts `sass` (`Dart Sass`) or `node-sass` as a module. #### `object` For example, to use Dart Sass, you'd pass: ```js module.exports = { module: { rules: [ { test: /\.s[ac]ss$/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: ```js module.exports = { module: { rules: [ { test: /\.s[ac]ss$/i, use: [ "style-loader", "css-loader", { loader: "sass-loader", options: { // Prefer `dart-sass` implementation: require.resolve("sass"), }, }, ], }, ], }, }; ``` Note that when using `sass` (`Dart Sass`), **synchronous compilation is twice as fast as asynchronous compilation** by default, due to the overhead of asynchronous callbacks. To avoid this overhead, you can use the [fibers](https://www.npmjs.com/package/fibers) package to call asynchronous importers from the synchronous code path. We automatically inject the [`fibers`](https://github.com/laverdet/node-fibers) package (setup `sassOptions.fiber`) for `Node.js` less v16.0.0 if is possible (i.e. you need install the [`fibers`](https://github.com/laverdet/node-fibers) package). > **Warning** > > Fibers is not compatible with `Node.js` v16.0.0 or later. Unfortunately, v8 commit [dacc2fee0f](https://github.com/v8/v8/commit/dacc2fee0f815823782a7e432c79c2a7767a4765) is a breaking change and workarounds are non-trivial. ([see introduction to readme](https://github.com/laverdet/node-fibers)). **package.json** ```json { "devDependencies": { "sass-loader": "^7.2.0", "sass": "^1.22.10", "fibers": "^4.0.1" } } ``` You can disable automatically injecting the [`fibers`](https://github.com/laverdet/node-fibers) package by passing a `false` value for the `sassOptions.fiber` option. **webpack.config.js** ```js module.exports = { module: { rules: [ { test: /\.s[ac]ss$/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** ```js module.exports = { module: { rules: [ { test: /\.s[ac]ss$/i, use: [ "style-loader", "css-loader", { loader: "sass-loader", options: { implementation: require("sass"), sassOptions: { fiber: require("fibers"), }, }, }, ], }, ], }, }; ``` ### `sassOptions` Type: ```ts type sassOptions = | import("sass").LegacyOptions<"async"> | (( content: string | Buffer, loaderContext: LoaderContext, meta: any ) => import("sass").LegacyOptions<"async">); ``` Default: defaults values for Sass implementation Options for [Dart Sass](http://sass-lang.com/dart-sass) or [Node Sass](https://github.com/sass/node-sass) implementation. > **Note** > > The `charset` option has `true` value by default for `dart-sass`, we strongly discourage change value to `false`, because webpack doesn't support files other than `utf-8`. > **Note** > > The `indentedSyntax` option has `true` value for the `sass` extension. > **Note** > > Options such as `data` and `file` are unavailable and will be ignored. > ℹ We strongly discourage change `outFile`, `sourceMapContents`, `sourceMapEmbed`, `sourceMapRoot` options because `sass-loader` automatically sets these options when the `sourceMap` option is `true`. > **Note** > > Access to the [loader context](https://webpack.js.org/api/loaders/#the-loader-context) inside the custom importer can be done using the `this.webpackLoaderContext` property. There is a slight difference between the `sass` (`dart-sass`) and `node-sass` options. Please consult documentation before using them: - [Dart Sass documentation](https://sass-lang.com/documentation/js-api/interfaces/Options) for all available `sass` options. - [Node Sass documentation](https://github.com/sass/node-sass/#options) for all available `node-sass` options. #### `object` Use an object for the Sass implementation setup. **webpack.config.js** ```js module.exports = { module: { rules: [ { test: /\.s[ac]ss$/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. ```js module.exports = { module: { rules: [ { test: /\.s[ac]ss$/i, use: [ "style-loader", "css-loader", { loader: "sass-loader", options: { sassOptions: (loaderContext) => { // More information about available properties https://webpack.js.org/api/loaders/ const { resourcePath, rootContext } = loaderContext; const relativePath = path.relative(rootContext, resourcePath); if (relativePath === "styles/foo.scss") { return { includePaths: ["absolute/path/c", "absolute/path/d"], }; } return { includePaths: ["absolute/path/a", "absolute/path/b"], }; }, }, }, ], }, ], }, }; ``` ### `sourceMap` Type: ```ts type sourceMap = boolean; ``` Default: depends on the `compiler.devtool` value Enables/Disables generation of source maps. By default generation of source maps depends on the [`devtool`](https://webpack.js.org/configuration/devtool/) option. All values enable source map generation except `eval` and `false` value. > ℹ If a `true` the `sourceMap`, `sourceMapRoot`, `sourceMapEmbed`, `sourceMapContents` and `omitSourceMapUrl` from `sassOptions` will be ignored. **webpack.config.js** ```js module.exports = { module: { rules: [ { test: /\.s[ac]ss$/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** ```js module.exports = { module: { rules: [ { test: /\.s[ac]ss$/i, use: [ "style-loader", "css-loader", { loader: "sass-loader", options: { sourceMap: true, sassOptions: { outputStyle: "compressed", }, }, }, ], }, ], }, }; ``` ### `additionalData` Type: ```ts type additionalData = | string | ((content: string | Buffer, loaderContext: LoaderContext) => string); ``` Default: `undefined` Prepends `Sass`/`SCSS` code before the actual entry file. In this case, the `sass-loader` will not override the `data` option but just **prepend** the entry's content. This is especially useful when some of your Sass variables depend on the environment: #### `string` ```js module.exports = { module: { rules: [ { test: /\.s[ac]ss$/i, use: [ "style-loader", "css-loader", { loader: "sass-loader", options: { additionalData: "$env: " + process.env.NODE_ENV + ";", }, }, ], }, ], }, }; ``` #### `function` ##### Sync ```js module.exports = { module: { rules: [ { test: /\.s[ac]ss$/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 ```js 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 "$value: 200px;" + content; }, }, }, ], }, ], }, }; ``` ### `webpackImporter` Type: ```ts type webpackImporter = boolean; ``` Default: `true` Enables/Disables the default Webpack importer. This can improve performance in some cases. Use it with caution because aliases and `@import` at-rules starting with `~` will not work. You can pass own `importer` to solve this (see [`importer docs`](https://github.com/sass/node-sass#importer--v200---experimental)). **webpack.config.js** ```js module.exports = { module: { rules: [ { test: /\.s[ac]ss$/i, use: [ "style-loader", "css-loader", { loader: "sass-loader", options: { webpackImporter: false, }, }, ], }, ], }, }; ``` ### `warnRuleAsWarning` Type: ```ts 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** ```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}: $value; } .tilt { // Oops, we typo'd "webkit" as "wekbit"! @include prefix(transform, rotate(15deg), wekbit ms); } ``` The presented code will throw webpack warning instead logging. To ignore unnecessary warnings you can use the [ignoreWarnings](https://webpack.js.org/configuration/other-options/#ignorewarnings) option. **webpack.config.js** ```js module.exports = { module: { rules: [ { test: /\.s[ac]ss$/i, use: [ "style-loader", "css-loader", { loader: "sass-loader", options: { warnRuleAsWarning: true, }, }, ], }, ], }, }; ``` ### `api` Type: ```ts type api = "legacy" | "modern"; ``` Default: `"legacy"` Allows you to switch between `legacy` and `modern` API. You can find more information [here](https://sass-lang.com/documentation/js-api). > **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](https://github.com/webpack-contrib/sass-loader/issues/774). > **Warning** > > The sass options are different for `modern` and `old` APIs. Please look at [docs](https://sass-lang.com/documentation/js-api) how to migrate on new options. **webpack.config.js** ```js module.exports = { module: { rules: [ { test: /\.s[ac]ss$/i, use: [ "style-loader", "css-loader", { loader: "sass-loader", options: { api: "modern", sassOptions: { // Your sass options }, }, }, ], }, ], }, }; ``` ## How to enable `@debug` output Defaults, the output of `@debug` messages is disabled. To enable it, add to **webpack.config.js** following: ```js module.exports = { stats: { loggingDebug: ["sass-loader"], }, // ... }; ``` ## Examples ### Extracts CSS into separate files For production builds it's recommended to extract the CSS from your bundle being able to use parallel loading of CSS/JS resources later on. There are two possibilities to extract a style sheet from the bundle: - [mini-css-extract-plugin](https://github.com/webpack-contrib/mini-css-extract-plugin) - [extract-loader](https://github.com/peerigon/extract-loader) (simpler, but specialized on the css-loader's output) **webpack.config.js** ```js const MiniCssExtractPlugin = require("mini-css-extract-plugin"); module.exports = { module: { rules: [ { test: /\.s[ac]ss$/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** ```javascript 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](https://medium.com/@toolmantim/getting-started-with-css-sourcemaps-and-in-browser-sass-editing-b4daab987fb0). Checkout [test/sourceMap](https://github.com/webpack-contrib/sass-loader/tree/master/test) for a running example. ## Contributing Please take a moment to read our contributing guidelines if you haven't yet done so. [CONTRIBUTING](./.github/CONTRIBUTING.md) ## License [MIT](./LICENSE) [npm]: https://img.shields.io/npm/v/sass-loader.svg [npm-url]: https://npmjs.com/package/sass-loader [node]: https://img.shields.io/node/v/sass-loader.svg [node-url]: https://nodejs.org [tests]: https://github.com/webpack-contrib/sass-loader/workflows/sass-loader/badge.svg [tests-url]: https://github.com/webpack-contrib/sass-loader/actions [cover]: https://codecov.io/gh/webpack-contrib/sass-loader/branch/master/graph/badge.svg [cover-url]: https://codecov.io/gh/webpack-contrib/sass-loader [chat]: https://badges.gitter.im/webpack/webpack.svg [chat-url]: https://gitter.im/webpack/webpack [size]: https://packagephobia.now.sh/badge?p=sass-loader [size-url]: https://packagephobia.now.sh/result?p=sass-loader