The Chrome User Experience Report (CrUX) is a public dataset of real-world performance metrics collected from opted-in Chrome users across millions of websites. Google uses CrUX field data to assess [Core Web Vitals](/glossary/core-web-vitals) for ranking purposes, so it reflects actual user conditions — varying devices, networks, and locations — rather than lab simulations. Data is aggregated at the origin and URL level and updated monthly. When a page lacks enough traffic for URL-level data, Google falls back to origin-level data for ranking assessments.