Tailwind CSS v4 ships with a completely new engine. Instead of a PostCSS-based pipeline, v4 relies on its own compiler written in Rust, which is significantly faster.
Configuration moves from JavaScript to CSS. Custom properties and native CSS features replace many of the previous JavaScript configurations. This makes the setup leaner and closer to web standards.
For existing projects, there is an automatic upgrade tool. Most breaking changes affect edge cases. The switch is worth it for the massively improved build performance alone.
