Results The timings for processing a 200 KB file of plain CSS (lower is better): Sass: 4.9 sec Sass: 2.5 sec (with warm .sass-cache) libsass: 0.2 sec Stylus: 1.7 sec Rework: 0.2 sec LESS: 0.5 sec r.js: 0.2 sec Libsass (a C++ implementation of Sass) and Rework turn out to be extremely fast. Background The speed of your CSS preprocessor is important for developer/designer ergonomics. The preprocessi