Chrome User Experience ReportCrUX

The Chrome User Experience Report is the source of truth for field performance. It aggregates real-user measurements, Core Web Vitals among them, from a sample of opted-in Chrome users browsing the live web, and exposes them through a public API, BigQuery dataset, and the CrUX dashboard. When Google says a page passes Core Web Vitals, it means the CrUX field data passes, not a lab tool.

The distinction between field and lab data is the most important thing to understand here. Lab tools like Lighthouse run a controlled, single synthetic load on a fixed device profile; they are reproducible and good for debugging. Field data reflects the messy reality of real devices, networks, and usage patterns. A page can score well in Lighthouse and still fail CrUX because real users are on slower phones and worse connections than the lab profile.

CrUX requires enough traffic to report; low-traffic pages fall back to origin-level data or have no field data at all. For those, lab data and the CrUX origin aggregate are the best available proxies. We always report both, and we label which is which, because conflating them is the most common way performance reporting misleads.