cnfast

Fast drop-in replacement for cn.

cnfast runs 25× faster than clsx + tailwind-merge across 58 real-world component repositories, with byte-identical output. Same API, no code changes.

import { cn } from "cnfast";

cn("px-2 py-1", isActive && "px-4", { "text-red-500": hasError });
// "py-1 px-4 text-red-500"

Install

npm install cnfast

Migrate an existing clsx, classnames, or tailwind-merge project in one command:

npx cnfast migrate

On a shadcn/ui project, add or replace your cn utility through the registry. This rewrites lib/utils.ts to re-export cnfast and installs the package:

npx shadcn@latest add aidenybai/cnfast/cn

Usage

Swap the shadcn/ui cn helper for cnfast:

// before
import { clsx, type ClassValue } from "clsx";
import { twMerge } from "tailwind-merge";
export const cn = (...inputs: ClassValue[]) => twMerge(clsx(inputs));

// after
export { cn } from "cnfast";

cnfast also exports clsx, twMerge, and twJoin.

Development

ni
nr build
nr test

License

MIT