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    sass-loader
    DefinitelyTyped icon, indicating that this package has TypeScript declarations provided by the separate @types/sass-loader package

    13.0.1 • Public • Published

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    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.

    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 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.

    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 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:

    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.

    If a true the sourceMap, sourceMapRoot, sourceMapEmbed, sourceMapContents and omitSourceMapUrl 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,
                },
              },
            ],
          },
        ],
      },
    };

    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) => {
                    // 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 and old 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 two 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",
        }),
      ],
    };

    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.

    CONTRIBUTING

    License

    MIT

    Install

    npm i sass-loader

    DownloadsWeekly Downloads

    11,223,924

    Version

    13.0.1

    License

    MIT

    Unpacked Size

    58 kB

    Total Files

    9

    Last publish

    Collaborators

    • evilebottnawi
    • sokra
    • jhnns