PostCSS

PostCSS is a tool for transforming stylesheets with JavaScript plugins. It comes with a parser that reads your CSS file into an AST, pipes it through the loaded plugins and finally stringifies it back into a (transformed) CSS output file.

We at AOE love PostCSS because it gives us the power to use CSS Modules, which finally ends the curse of global CSS.

It also has a huge list of more than 350 other available plugins. Sure, not all of them are useful, but the sheer number of plugins shows how easy it is to write your own plugin for it. In fact, it´s just a matter of writing a single JS function.

Finally, PostCSS is very fast and easy to setup because it runs 100% in JavaScript. Compared to Sass as a preprocessor, it feels much more powerful but at the same time less bloated with superfluous functionality because everything comes in its own little plugin