shadcn/ui

shadcn/ui provides a set of accessible, customizable UI components built with React and Tailwind CSS. Rather than distributing them as a typical npm package you import as an opaque dependency, the project describes itself as "open code" meant to be used as a starting point: you bring the component source into your own project and customize, extend, and build on it directly, effectively using shadcn/ui to build your own component library rather than depending on an external one.

It's MIT licensed and documented at ui.shadcn.com, where the available components and usage patterns are covered in detail.

It's a fit for teams that want full ownership and control over their component code and styling from day one, rather than working around the constraints or theming system of a traditional, install-as-a-dependency component library.