shadcn releases 'cn' to speed up Tailwind class merging by 30x

cn drops into your Tailwind stack, replaces clsx and tailwind-merge, and runs 30 times faster with zero API changes.

Developers shadcn and aidenybai released cn, a zero-dependency engine for merging Tailwind classes and resolving conflicts. It provides exact parity with tailwind-merge and clsx across 356,000 differential tests, but optimizes execution to skip redundant string work. It works with any framework and any Tailwind CSS v4 project—no shadcn/ui components required.

Why it matters: For standard component calls, cn handles class merging in 10 nanoseconds compared to 320 nanoseconds with traditional setups. Benchmarks replaying calls across 58 open-source repositories show cn runs 37× faster on average while shipping a small 26 KB minified bundle. That means faster client renders and lighter edge execution without rewriting your existing components.

To switch, run npx shadcn@latest migrate cn or install it directly with npm i cn. In existing projects, update your @/lib/utils file to export { cn } from "cn" and remove clsx and tailwind-merge from your package dependencies.

Your component syntax stays identical, but your render loop just got a massive speed boost.