PostCSS is a software development tool that uses JavaScript-based plugins to automate routine CSS operations.

[3] It was designed by Andrey Sitnik with the idea taking its origin in his front-end work for Evil Martians.

There are official tools making it possible to use PostCSS with build systems such as Webpack,[8] Gulp,[9] and Grunt.

What it does is change the original files — for instance, by sorting the CSS properties or checking the code for mistakes.

[15] PostCSS plugins perform different CSS processing tasks ranging from analysis and properties sorting to minification.

During the course of the Rework project, the idea of modular CSS processing was suggested by TJ Holowaychuk September 1, 2012.

[29] March 14, 2013, Andrey Sitnik's front-end work for Evil Martians resulted in Autoprefixer, a Rework-based plugin.