eleventy-sass

Yet another Sass/SCSS plugin for Eleventy.

Source maps, PostCSS and revision hashes are supported.

Why another Sass plugin?

There are several Eleventy plugins to support Sass/SCSS files, already. Even the official Eleventy website has a page which describes how to handle Sass/SCSS files with your Eleventy project.

I created the plugin, because I was not satisfied with the above solutions, for example:

• The existing plugins did watch Sass/SCSS files and write CSS files by themselves or by using another toolkit, such as gulp.js, instead of using Eleventy's file watching and writing functionality. They might work well, but doesn't seem to be integrated enough with Eleventy.

• The page in the official Docs is great if you only have Sass/SCSS files which do not have @use or @forward rules.
  If you use @use in your Sass/SCSS files, for example, and you change a dependency Sass/SCSS file, Eleventy will compile it (if its filename doesn't start with "_"), but won't compile the dependant Sass/SCSS files, if you are following the instructions in the page of the official Docs.

In contrast to the existing solutions, eleventy-sass manages dependencies between Sass/SCSS files and makes maximum use of Eleventy's functionality. It is highly configurable, but it just works if you add it in your Eleventy config file.

For those of you who are curious about how eleventy-sass handles Sass/SCSS files, here is a brief explanation.

Installation

npm install eleventy-sass

For Eleventy 3, install eleventy-sass@3.0.0-beta.x as follows:

npm install eleventy-sass@^3.0.0-beta.0

eleventy-sass@3.0.0-beta.x requires Node.js >= 22.

Usage

Open up your Eleventy config file (probably .eleventy.js) and use addPlugin():

const eleventySass = require("eleventy-sass");

module.exports = function(eleventyConfig) {
  eleventyConfig.addPlugin(eleventySass);
};

That's it. Only the above code in your .eleventy.js, your Sass/SCSS files will be compiled to CSS and written in your output directory.

For Eleventy 3 users

eleventy-sass@3.0.0-beta.x uses an experimental feature of Node.js 22 to load Eleventy 3 internal modules. You should add --experimental-require-module option to your Node commands.

Therefore, instead of running npx @11ty/eleventy, use the following command:

npx --node-options="--experimental-require-module" @11ty/eleventy

Default behavior

Suppose your have the following .eleventy.js. In this example, your input directory is "src" and your output directory is "dist" since it seems to be widely used settings in Eleventy community.

const eleventySass = require("eleventy-sass");

module.exports = function(eleventyConfig) {
  eleventyConfig.addPlugin(eleventySass);

  return { dir: { input: "src", output: "dist" } };
};

and execute npx @11ty/eleventy or npx @11ty/eleventy --serve from your shell, you will get the following:

├── .eleventy.js
├── dist
│   ├── index.html
│   └── stylesheets
│       ├── accessibility
│       │   └── large-style.css
│       └── style.css
├── package-lock.json
├── package.json
└── src
    ├── _includes
    │   └── tag-cloud.scss
    ├── index.md
    └── stylesheets
        ├── accessibility
        │   └── large-style.scss
        ├── style.scss
        └── themes
            └── _gruvbox.scss

As you can see, your Sass/SCSS files in your input ("src") directory, no matter how deep they are, were compiled and written in your output ("dist") directory unless they are in includes ("_includes") directory or their filenames start with "_".

Files in includes directory and files whose filenames start with "_" are not compiled directly but can be used from the other Sass/SCSS files with @use and @forward rules.

For example, _gruvbox.scss file in the above example can be loaded from style.scss file with @use "themes/gruvbox";, and tag-cloud.scss file can be loaded from style.scss file with @use "tag-cloud";. (The reason you don't have to specify it with @use "../_includes/tag-cloud"; is that includes ("_includes") directory is the default loadPaths for eleventy-sass. I will describe loadPaths in Sass options.)

For Windows users

Command samples in this documentation suppose Linux/macOS environments.

ELEVENTY_ENV=development npx @11ty/eleventy

Please replace, for example, the above command with the following:

set ELEVENTY_ENV=development & npx @11ty/eleventy

in cmd.exe or

$env:ELEVENTY_ENV="development"; npx @11ty/eleventy

in PowerShell.

Options

eleventy-sass allows you to customize the behavior by options like follows:

// .eleventy.js
const eleventySass = require("eleventy-sass");

module.exports = function(eleventyConfig) {
  eleventyConfig.addPlugin(eleventySass, {
    compileOptions: {
      permalink: function(contents, inputPath) {
        return (data) => data.page.filePathStem.replace(/^\/scss\//, "/css/") + ".css";
      }
    },
    sass: {
      style: "compressed",
      sourceMap: false
    },
    rev: true
  });
};

Options can be of type Object or Array.

Options object

Let's talk about passing an object as options first.

Basically, options you pass as the second argument for addPlugin() is used for options for eleventyConfig.addExtension(), which eleventy-sass calls internally. The full options list is provided in the official Docs.

However, there are exceptions. Four properties, which are sass, postcss, rev and when, are not used for options for eleventyConfig.addExtension() but used for other purposes.

sass property

sass property is used for options for sass.compileString(), a dart-sass API function, which eleventy-sass calls internally. For details, please read Sass options and the Sass documentation.

postcss property

You can set PostCSS object to postcss property, and eleventy-sass automatically apply the PostCSS object to the compiled CSS files.

// .eleventy.js
const eleventySass = require("eleventy-sass");
const postcss = require("postcss");
const rtlcss = require("rtlcss");
const cssnano = require("cssnano");

module.exports = function(eleventyConfig) {
  eleventyConfig.addPlugin(eleventySass, {
    postcss: postcss([rtlcss, cssnano])
  });
};

rev property

If you want to add revision hashes to the compiled CSS filenames, you can set true to rev property and add eleventy-plugin-rev as follows:

npm install eleventy-plugin-rev

// .eleventy.js
const pluginRev = require("eleventy-plugin-rev");
const eleventySass = require("eleventy-sass");

module.exports = function(eleventyConfig) {
  eleventyConfig.addPlugin(pluginRev);
  eleventyConfig.addPlugin(eleventySass, {
    rev: true
  });
};

You can use filter functions, rev and revvedOutput, to add revision hashes.

Suppose you have the following project (input directory is src and output directory is dist):

.
├── .eleventy.js
├── dist
│   ├── blog
│   │   └── eleventy-quick-tips/index.html
│   ├── css
│   │   └── style-42df228b.css
│   └── index.html
└── src
    ├── index.md
    ├── blog
    │   └── eleventy-quick-tips.md
    └── scss
        └── style.scss

The link tag to your CSS file will be the following:

By using filters, you can write the above link tag as follows:

⚠️ The paths for the rev and revvedOutput filters must be relative from the output and input directories respectively and must be prefixed with /, or a relative path from the current file.

For example, from eleventy-quick-tips.md file, you can also write the link tag as follows:

⚠️ inputToRevvedOutput filter will be deprecated. (Input paths for inputToRevvedOutput must be relative paths from your project root, even if your input directory is not your project root.)

when property

when property is a special property, which is used for enabling or disabling the options object by environment/shell variables. For details, see when options.

Options array

You can set an array of objects to the second argument of addPlugin() to configure eleventy-sass with a finer granularity.

In this case, each element of the array is an options object.

First, eleventy-sass concatenates the default options and user-defined options.

I didn't write about it in the above Options object section, but even if you set an object as options, the plugin concatenates the default options and the user-defined options object(s) and the following process is exactly the same.

Elements of the array are options objects, and each object is enabled or disabled by its when property. If the evaluation of the when property is false, an options object will be disabled.

After the evaluations, eleventy-sass merges all of the enabled options of the array, which was created from default options objects and user-defined options objects, and create a final options object.

When merging, elements at greater indexes can overwrite elements at smaller indexes. So, the default options are weakest and the last element of a user-defined options array is the strongest, and the default options can be overwritten by user-defined options.

Therefore, in general, general options should be placed at smaller indexes and more specific (conditional) options should be placed at greater indexes.

Let's take a look at an example:

// .eleventy.js
const eleventySass = require("eleventy-sass");

module.exports = function(eleventyConfig) {
  eleventyConfig.addPlugin(eleventySass, [
    {
      compileOptions: {
        permalink: function(permalinkString, inputPath) {
          return (data) => {
            return data.page.filePathStem.replace(/^\/scss\//, "/css/") + ".css";
          };
        }
      },
      sass: {
        style: "expanded",
        sourceMap: true
      }
    }, {
      rev: true,
      when: { ELEVENTY_ENV: "stage" }
    }, {
      sass: {
        style: "compressed",
        sourceMap: false
      },
      rev: true,
      when: [ { ELEVENTY_ENV: "production" }, { ELEVENTY_ENV: false } ]
    }
  ]);
};

The first element defines permalink, style and sourceMap, and it should be applied in whichever environments because there is no when property.

The second element defines rev, and it should be applied only when ELEVENTY_ENV environment/shell variable is stage.

The last element defines style, sourceMap and rev, and it should be applied when ELEVENTY_ENV is production or ELEVENTY_ENV is not defined (or ELEVENTY_ENV is an empty string).

Therefore, when you run ELEVENTY_ENV=development npx @11ty/eleventy --serve in Linux/macOS terminal for example, the result CSS files have source maps and expanded style (because of the first options object), but their filenames do not have revision hashes, because the second and the third options objects are disabled.

When you run ELEVENTY_ENV=stage npx @11ty/eleventy --serve, the result CSS files have source maps and expanded style (because of the first options object), and their filenames have revision hashes (because of the second options object).

When you run npx @11ty/eleventy --serve (if ELEVENTY_ENV is not defined in .bashrc, .zshrc, etc.), ELEVENTY_ENV=production npx @11ty/eleventy --serve or ELEVENTY_ENV= npx @11ty/eleventy --serve, the result CSS files do not have source maps and have compressed style and their filenames have revision hashes (because of the last options object).

Default options

If you do not specify any options, eleventy-sass uses the default options.

// Default options
[
  {
    compileOptions: {
      cache: true,
    },
    sass: {
      includes: [/* The includes directory of your Eleventy project */],
      style: "expended",
      sourceMap: true,
      sourceMapIncludeSources: true
    }
  }, {
    sass: {
      style: "compressed",
      sourceMap: false
    },
    when: { ELEVENTY_ENV: (env) => env === undefined || "production".startsWith(env) }
  }
]

The above is the default options. In short, they say eleventy-sass writes minified (compressed) CSS files without source maps if ELEVENTY_ENV environment/shell variable is production or not set, otherwise writes readable (expanded) CSS files with source maps.

For example, if you add the following line in your .bash_profile, .bashrc, .zshrc, etc. on your local PC,

export ELEVENTY_ENV=development

the environment is development locally, and the result CSS files will have readable style and source maps, because the second element of the default options is disabled and the only first options object is applied.

On the other hand, you will have CSS files with compressed style and without source maps, for example, in GitHub Actions by default, because there is no ELEVENTY_ENV environment variable and the second element of the default options is enabled.

And, of course, you can specify an environment from your shell prompt like this:

ELEVENTY_ENV=production npx @11ty/eleventy --serve

Some recipes

How to change output directory for CSS files compiled from Sass/SCSS

For example, you have Sass/SCSS files in scss directory in your input directory. To output CSS files in css directory in your output directory, you can write a permalink function like this:

const eleventySass = require("eleventy-sass");

module.exports = function(eleventyConfig) {
  eleventyConfig.addPlugin(eleventySass, {
    compileOptions: {
      permalink: function(contents, inputPath) {
        return (data) => {
          return data.page.filePathStem.replace(/^\/scss\//, "/css/") + ".css";
        };
      }
    }
  });
};

For details, please refer to the compileOptions.permalink section in the official documentation.

How to use PostCSS and Autoprefixer to add vender prefixes

Install PostCSS and Autoprefixer

npm install postcss autoprefixer

Configure your .eleventy.js as follows:

const eleventySass = require("eleventy-sass");
const postcss = require("postcss");
const autoprefixer = require("autoprefixer");

module.exports = function(eleventyConfig) {
  eleventyConfig.addPlugin(eleventySass, {
    postcss: postcss([autoprefixer])
  });
};

Edit your package.json, for example:

{
  // ...
  "browserslist": [
    "last 1 chrome version",
    "last 1 firefox version",
    "last 1 safari version",
    "last 1 ie version"
  ]
  // ...
}

See Autoprefixer and Browserslist for more details.

Debug mode

You can see verbose outputs by using DEBUG environment/shell variable (cf. DEBUG MODE).

DEBUG=Eleventy* npx @11ty/eleventy

If you want to see only the eleventy-sass's verbose outputs, change the value for DEBUG environment/shell variable like this:

DEBUG=EleventySass* npx @11ty/eleventy

or, if you prefer more verbose outputs, like this:

DEBUG=*EleventySass* npx @11ty/eleventy

How eleventy-sass handles Sass/SCSS files

Eleventy watches files.

When Eleventy detects a file update, it emits an eleventy.beforeWatch event, and eleventy-sass will receive the event and check if the file is a Sass/SCSS file.

If the file is a Sass/SCSS file, eleventy-sass changes the cache keys for the updated file and its dependant Sass/SCSS files, which invalidates the cached CSSes, so that Eleventy will compile all of the files affected.

When compiling Sass/SCSS files, Eleventy calls compile function of the eleventy-sass.

The compile function of eleventy-sass will compile Sass/SCSS files if they don't start with "_".

The actual compilation is done by sass, which is dart-sass.

By using the result of the compilation from dart-sass, eleventy-sass not only returns the compiled CSS, but also, if necessary, writes its source map file and updates the dependency map, which eleventy-sass has internally and uses for invalidating cached CSSes of dependant files as described above.