What is it?

Tailwind CSS v4 is a ground-up rewrite of the utility-first CSS framework, powered by a new Rust-based engine (Lightning CSS). The biggest shift: configuration moves from tailwind.config.js to CSS-native @theme directives. Content detection is automatic — no more configuring content paths. Build times are 5-10x faster than v3.

Why does it matter?

Tailwind v3 was already dominant, but the JavaScript-based toolchain added build complexity and performance overhead. v4 fixes both. The CSS-first configuration means your theme lives in a .css file, not a JS config — it’s more portable and easier to reason about. Automatic content detection eliminates the most common source of “why isn’t my class working?” frustration.

Trade-offs

Strengths:

  • 5-10x faster builds via Rust-based engine
  • CSS-first config with @theme — no more tailwind.config.js
  • Automatic content detection (no content array to maintain)
  • Built-in import support without PostCSS plugins
  • Container queries, @starting-style, and modern CSS features natively supported

Limitations:

  • Migration from v3 requires config rewrite and some class name changes
  • Plugin ecosystem is still adapting to the new architecture
  • Some v3 plugins don’t have v4 equivalents yet
  • CSS-first config is a paradigm shift that takes adjustment

Our take

Tailwind v4 moved to Trial because the developer experience improvement is substantial, but the ecosystem needs time to catch up. For new projects, start with v4 — the faster builds and simpler config are worth it. For existing v3 projects, wait until your key plugins support v4 before migrating. The upgrade path is well-documented but not trivial.