Tailwind CSS v4 shifts from the plugin system of v3 toward a CSS-first configuration model built on native cascade layers.
What changed
The biggest change is that configuration now lives in plain CSS using the @theme directive, which makes theming simpler and removes most JavaScript setup from your build pipeline.
@theme {--color-primary: #2563eb;}Migration checklist
Update your PostCSS configuration, move tailwind.config.js values into CSS variables, and run the upgrade tool to find deprecated utilities.