Bootstrap is the more common of the two in our index: it runs on 9,427 websites against 27 for Materialize CSS, and 4 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.
Materialize CSS is a front-end framework that helps developers create responsive and mobile-first web applications. It is based on Google's Material Design guidelines.
4 sites run both Bootstrap and Materialize CSS. That is 15% of the sites using Materialize CSS, 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.