Comment by jokull

"Bring your own UI". You get the behavior from the library but they are completely unstyled or without the component layer where the styles live. Other libraries include Radix and HeadlessUI. Here's a presentation from one of the Radix library authors about how to build dropdowns in React, it serves as a good explainer about what goes into a headless UI library component. https://www.youtube.com/watch?v=lY-RQjWeweo