React is the more common of the two in our index: it runs on 9,540 websites against 5,071 for Next.js, and 5,071 sites use both. Counts come from real scans, not vendor claims.
Next.js is a React framework for developing single page Javascript applications.
React is an open-source JavaScript library for building user interfaces or UI components.
5,071 sites run both Next.js and React. That is 100% of the sites using Next.js, 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.