Tailwind CSS v4 was released in January 2025 and represents the most significant change in the framework's history. This isn't about incremental additions — it's a deep rewrite that changes how we think about configuration, theming and integration with modern tooling.
Goodbye tailwind.config.js
The most impactful change: configuration moves entirely to the CSS file. No more tailwind.config.js — everything now lives in @theme, a native CSS directive Tailwind introduces to define the design token system.
Before (v3)
In v3, the JavaScript configuration file defined colours, fonts, breakpoints and every aspect of the design system. A functional approach but one that required leaving CSS to manage CSS.
Now (v4)
With @theme, tokens live in the CSS itself as custom properties. The result is a more coherent and intelligible system where all design is defined in one place — the stylesheet.
Performance: 5x faster builds
The new engine, rewritten in Rust, brings drastic improvements: full builds up to 5x faster than v3, and incremental builds over 100x faster. In a real medium-sized project, this means going from 800ms to under 100ms for a rebuild.
- Full build: up to 5x faster
- Incremental build: over 100x faster
- Significantly reduced memory usage
- No PostCSS dependency (optional in v4)
Native Vite plugin
Tailwind v4 introduces @tailwindcss/vite, a native Vite plugin that replaces the need to configure PostCSS. Integration is immediate and brings even better performance to the development server.
We updated this very site to Tailwind v4 during development. Build time went from 2.1s to 0.4s. The developer experience improved noticeably.
Compatibility and migration
Migrating from v3 to v4 requires some care. Existing utility classes are almost all compatible, but the configuration needs rewriting. The Tailwind team has released an automatic migration tool that handles most cases.
Is it worth upgrading?
For new projects: absolutely yes, start directly with v4. For existing projects: evaluate the migration cost. On medium-sized projects the cost is low (2-4 hours) and the benefits in terms of DX and build time are immediate.