Tailwind CSS v4.0

Source: Tailwind Labs Date: 2025-01-22 URL: https://tailwindcss.com/blog/tailwindcss-v4

Summary

Ground-up engine rewrite shipping January 2025. Full builds 3.78x faster, incremental builds 8.8x faster, no-change builds 182x faster. CSS-first configuration replaces tailwind.config.js — theme customization moves to @theme {} blocks in CSS. Single @import "tailwindcss" replaces multi-directive setup; automatic content detection drops the content array.

Implications

• Oxide engine arc. The v4 engine (Rust-backed, Lightning CSS under the hood) closes the gap between Tailwind’s JIT and native CSS tooling in raw build speed. At sub-100ms full builds, the remaining friction argument for switching to UnoCSS or raw PostCSS pipelines weakens further.
• CSS-first config is a positioning shift. Moving configuration into CSS makes Tailwind feel more like a CSS preprocessor than a JS tool. This lowers the barrier for designers comfortable in CSS but unfamiliar with tailwind.config.js — and removes one of UnoCSS’s ergonomic talking points.
• Breaking change surface. Removed deprecated utilities, changed border and ring defaults, PostCSS plugin and CLI now separate packages. Ecosystem tooling (Tailwind UI templates, Catalyst components, IDE plugins) needed coordinated updates — watch adoption lag in downstream projects.
• oklch color space adoption. Default palette moved from sRGB to oklch. Signals Tailwind Labs treating modern CSS as a baseline, not a progressive enhancement — consistent with the broader design tooling shift toward P3-wide color.