Base UI is a headless (unstyled) React component library that provides low-level UI building blocks for creating fully custom user interfaces. It is designed for developers and teams who want complete control over styling while still benefiting from prebuilt, production-ready interaction logic and accessibility features.

The library abstracts complex UI behaviors such as keyboard navigation, focus management, positioning, and ARIA accessibility patterns into reusable components and hooks. Instead of dictating visual design, Base UI focuses entirely on functionality and structure, allowing developers to apply any styling solution they prefer, including Tailwind CSS, CSS Modules, CSS-in-JS, or plain CSS.

Base UI is built with a strong emphasis on accessibility and follows WAI-ARIA Authoring Practices as well as WCAG standards. It is designed to work across modern browsers and React environments, and it prioritizes composability, meaning developers can easily extend or replace internal component parts to fit custom design systems.

The project originates from the creators of Material UI, Radix UI, and Floating UI, and is positioned as a more flexible, “headless” alternative to traditional component libraries. It is especially useful for teams building custom design systems that require both accessibility compliance and full visual control.

Key features include:

• Unstyled, headless React components with no default CSS
• Built-in accessibility patterns (ARIA, keyboard navigation, focus control)
• Highly composable component APIs for full customization
• Compatibility with any styling solution (Tailwind, CSS Modules, etc.)
• Low-level hooks for building fully custom UI components

Common use cases include:

• Building custom design systems
• Creating accessible UI components from scratch
• Developing complex interactive elements (dialogs, menus, popovers)
• Standardizing UI behavior across large React applications

Base UI is developed and maintained by the MUI team (Material UI ecosystem) as an open-source project under the MIT license.