cn

cn is a drop-in replacement for the two utilities almost every Tailwind project uses to build class names: tailwind-merge and clsx. Same APIs, same output, one dependency instead of two, and it is markedly faster (roughly 30x on the call your components make most, by its own benchmarks). Built by shadcn and Aiden Bai, MIT, zero dependencies.

If you have ever written a cn helper in a shadcn/ui project, this replaces the guts of it. It merges conflicting Tailwind classes and joins conditional ones, verified against tailwind-merge with hundreds of thousands of differential tests, so behavior matches. It is framework-agnostic (React, Vue, Svelte, Solid, Astro, plain templates) and runs anywhere JS runs. Migration is one CLI command or a two-line edit to your utils file.

For most projects this is an easy swap: less to ship, faster class merging, same behavior. The catch is that the win is real but small in absolute terms, class merging is rarely your bottleneck, so do not expect a visible speedup in a normal app. Two caveats: it needs Tailwind v4 (stay on tailwind-merge v2 for v3), and it is new, so the ecosystem trust that tailwind-merge earned over years is not there yet.