Sass is a stylesheet language that's compiled to CSS. It allows you to use [variables][], [nested rules][], [mixins][], [functions][], and more, all with a fully CSS-compatible syntax. Sass helps keep large stylesheets well-organized and makes it easy to share design within and across projects. [variables]: /documentation/variables [nested rules]: /documentation/style-rules#nesting [mixins]: /documentation/at-rules/mixin [functions]: /documentation/functions * If you're looking for an introduction to Sass, check out [the tutorial](/guide). * If you want to look up a built-in Sass function, look no further than [the function reference](/documentation/functions). * If you're calling Sass from JavaScript, you may want the [JS API documentation][]. * Or the [Dart API documentation][] if you're calling it from Dart. * Otherwise, look to the left for the table of contents for the language reference! [JS API documentation]: https://github.com/sass/node-sass#usage [Dart API documentation]: https://pub.dartlang.org/documentation/sass/latest/sass/sass-library.html