Ruby Sass was the original implementation of Sass, but it reached its end of life as of 26 March 2019. It's no longer supported, and Ruby Sass users should migrate to another implementation.
When Natalie and Hampton first created Sass in 2006, Ruby was the language at the cutting edge of web development, the basis of their already-successful Haml templating language, and the language they used most in their day-to-day work. Writing Sass in Ruby made it readily available to their existing users and the whole booming Ruby ecosystem.
Since then, Node.js has become ubiquitous for frontend tooling while Ruby has faded into the background. At the same time, Sass projects have grown far larger than we initially envisioned them, and their performance needs have outpaced the speed Ruby can provide. Both Dart Sass and LibSass are blazing fast, easy to install, and are readily available on npm. Ruby Sass couldn't keep up, and it didn't make sense to spend the core team's resources on it any longer.
If you run Ruby Sass using the command-line
sassexecutable, all you need to do is install Dart Sass's command-line executable instead. The interface isn't identical, but most options work the same way.
If you use the
sassgem as a library, the
sasscgem is the most seamless way to move away from Ruby Sass. It uses LibSass to provide the same API for compiling Sass and defining custom functions as Ruby Sass, except that it uses the
SassCmodule instead of
Sass. However, it doesn't yet support the same
ImporterAPI. You can also use the
sassc-railsgem to plug smoothly into Ruby on Rails.