postcss/postcss

PostCSS is a tool that processes CSS files using JavaScript plugins. Think of it as a pipeline: your stylesheet goes in, PostCSS parses it into an internal representation (called an Abstract Syntax Tree, or AST, a structured map of every rule, property, and value), and then plugins transform that structure before it is written back out as CSS. The tool itself does not change your CSS directly; all the work is done by the plugins you choose. Over 200 plugins exist covering a wide range of tasks. Some of the most common: Autoprefixer automatically adds browser-specific prefixes so a CSS property works across different browsers without you writing the same rule multiple times. Stylelint checks your stylesheets for errors and style violations. Plugins also exist for minifying CSS, supporting nested rules (writing child styles inside parent styles), using CSS syntax features that browsers don't yet support, isolating styles to specific components so they don't accidentally affect other parts of a page, and handling right-to-left language layouts. PostCSS can also parse other stylesheet languages like Sass, Less, SCSS, and CSS embedded in JavaScript template strings. A front-end developer would use PostCSS as part of a build process, typically alongside a bundler, to automatically clean up, extend, or validate CSS as part of preparing a site for production. It runs on TypeScript and Node.js.