shadcn/ui

The dominant copy-own component model: Radix primitives + Tailwind.

shadcn/ui is a collection of reusable React components built on Radix UI primitives and styled with Tailwind CSS. Rather than being installed as a dependency, components are copied into the project via a CLI so developers fully own and customize the source. It is notable for popularizing the copy-paste, code-ownership model for component libraries and is widely used in the Next.js/React ecosystem.