Term
CrUX (Chrome User Experience Report)
CrUX is Google's public field-data dataset of real performance values from Chrome users (opt-in). It's the source of Core Web Vitals scoring in Search Console and PageSpeed Insights — not synthetic.
CrUX — explained in more detail
The Chrome User Experience Report collects anonymized performance telemetry from Chrome users who have opted in to data collection. Aggregated per origin (domain) and partly per URL, CrUX delivers real LCP, INP, CLS, FCP, and TTFB values from the field — the basis on which Google scores Core Web Vitals.
CrUX is accessible through several interfaces: PageSpeed Insights (online tool), the CrUX API (programmatic), and CrUX BigQuery (public dataset, monthly). Data is rolling 28 days; origin-level data is available once a site has enough traffic — very small sites often have no sufficient CrUX data (“not enough data”).
Example / In practice
A developer optimizes LCP locally to 1.2 s in a Lighthouse test. But PageSpeed Insights shows CrUX LCP at 4.1 s — real users have slower devices and weaker networks. Lab values alone aren’t enough; CrUX reflects reality.
Distinction from similar terms
Lighthouse provides lab data (synthetic, controlled conditions). RUM (Real User Monitoring) is conceptually the same as CrUX but from third parties (Cloudflare, Sentry, etc.) — your own RUM can also capture URLs that don’t have enough traffic for CrUX.
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