21st.dev

21st.dev is an open-source community registry for React UI components, often described as the npm for design engineers. It offers a large library of community-contributed, shadcn/ui-based components built with Tailwind CSS and Radix UI that you can install with a single npx command. It also includes an AI-powered Magic agent that generates multiple UI component variations from a prompt, plus MCP support for integration with AI coding tools like Cursor and Windsurf. Great for developers and designers who want production-ready, reusable components without building everything from scratch.