Bootstrap is the more common of the two in our index: it runs on 9,416 websites against 8 for Flowbite, and 2 sites use both. Counts come from real scans, not vendor claims.
Bootstrap is a free and open-source CSS framework directed at responsive, mobile-first front-end web development. It contains CSS and JavaScript-based design templates for typography, forms, buttons, navigation, and other interface components.
Flowbite is an open-source library of UI components based on the utility-first Tailwind CSS framework featuring dark mode support, a Figma design system, and more.
2 sites run both Bootstrap and Flowbite. That is 25% of the sites using Flowbite, the smaller of the two.
Want to know which one a particular site uses? Look it up and see its whole stack, or compare two sites side by side.