Tailwind CSS

Tailwind CSS is a highly popular, utility-first CSS framework designed for rapidly building custom user interfaces directly in your markup. The current stable release series is v4.2.2, which represents a significant architectural shift with a new, faster Rust-based engine (Oxide and Lightning CSS) for processing CSS. It has an active release cadence with frequent patch and minor updates. Key differentiators for v4 include its move towards a "CSS-first" configuration model, where customization is primarily handled within CSS files using `@theme` directives, and automatic content detection, simplifying the build process. Unlike previous versions, Tailwind CSS v4 no longer requires PostCSS for its core compilation, as it integrates its own CSS processing pipeline. Dedicated bundler plugins like `@tailwindcss/vite` and `@tailwindcss/webpack` are provided for seamless integration into modern build ecosystems, while still offering a PostCSS compatibility layer via `@tailwindcss/postcss` for existing setups. This version emphasizes performance, a smaller footprint, and leverages modern CSS features like native cascade layers and `color-mix()` for enhanced capabilities and developer experience.