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Sass (short for syntactically awesome style sheets) is a preprocessor scripting language that is interpreted or compiled into Cascading Style Sheets. It is a program that takes one data type (Sass) and converts it to another (CSS) Sass is fully compatible with all versions of CSS. There are other preprocessors like LESS, Stylus, but at the moment, Sass is the most popular. You don’t need to know Ruby or be an expert in the command line to use Sass.