radix-ui/primitives

Radix Primitives is an open-source library of low-level UI components for React, focused on accessibility and customization. "Primitives" here means the raw building blocks, things like dialogs, dropdowns, checkboxes, tooltips, and tabs, without any visual styling applied. This is deliberate: it handles the complex, hard-to-get-right behavior (keyboard navigation, screen reader support, focus management, correct ARIA attributes for accessibility) while leaving the visual appearance entirely up to you. The problem Radix solves: building accessible UI components correctly is surprisingly difficult. A dropdown menu, for example, needs to trap focus when open, respond to keyboard shortcuts, announce itself to screen readers, close when you click outside, and handle dozens of edge cases. Doing all of this from scratch for every component in an app takes weeks. Radix provides these behaviors pre-built and tested, so you can style the components however you want without worrying about accessibility regressions. You would use Radix Primitives when building a React web application where you want to implement your own visual design system but don't want to rebuild all the accessibility and interaction behavior yourself. It's commonly used as the foundation for design systems at companies and is the underlying base for popular component libraries like shadcn/ui. The library is written in TypeScript and maintained by WorkOS.