CSS is a powerful styling language whose feature set is constantly evolving, that allows incredible flexibility when designing websites. However, maintaining the structure, compatibility, and efficiency of stylesheets can become problematic, especially as projects grow.
Various CSS processing tools aim to address the shortcomings of the language with different approaches. Either by adding features to the language, modifying the syntax, or optimizing already written CSS. Of course, Browsers only understand the spec-compliant official version of CSS, so whatever a processor is doing has to happen before the client evaluates the CSS stylesheet.
This chapter will delve into commonly used features, present a few of the most popular CSS processors and cover the integration of CSS processors into web development toolchains.