CrUX Report(CrUX)

Long definition

CrUX is the public face of Google's real-user monitoring program. Chrome users who have opted in (via Chrome's "Make searches and browsing better" setting and meeting other criteria like syncing history without a custom passphrase) contribute performance metrics from their browsing sessions. The data is anonymized, aggregated to URL or origin level, and published via several access points.

Metrics published in CrUX:

• LCP, CLS, INP — the Core Web Vitals
• FCP, TTFB — diagnostic metrics
• Form factor (mobile vs desktop), connection type (4G, 3G, etc.), country

Reporting threshold: at the 75th percentile of users. A URL passes "Good LCP" if 75% of real-user samples come in under 2.5s. The 75th percentile is what Google uses for ranking, what PSI displays, and what shows up in Search Console.

Access points:

• PageSpeed Insights — single-URL or single-origin lookup
• CrUX Dashboard — Looker Studio frontend for monthly origin data
• CrUX BigQuery dataset — full historical data, free with a Google Cloud account
• CrUX History API — last 25 weeks per URL via REST, no quota for normal use
• Search Console Core Web Vitals report — site-owner-facing summaries

Window: 28-day rolling for the API and PSI. BigQuery publishes monthly snapshots aligned to calendar months.

The data threshold is the catch. A URL needs ~1,000+ samples in the 28-day window to appear at URL granularity. Below that, CrUX falls back to origin-level data or returns no data. New URLs, long-tail product pages, and low-traffic sites are routinely "no field data available" — which forces those teams to rely on lab metrics or private RUM.

Common misconceptions

• "CrUX measures my whole site." It measures public URLs visited by opted-in Chrome users. Authenticated pages, intranet apps, and pages behind login walls aren't in CrUX. Same for non-Chrome traffic — Safari, Firefox, Edge users don't contribute.
• "CrUX uses the median." It uses the 75th percentile for "good" thresholds. A URL where 60% of users see good LCP and 40% see poor LCP fails — because the 75th percentile sample is in the poor bucket.
• "BigQuery CrUX data is the same as PSI." BigQuery is monthly, calendar-aligned. PSI and the CrUX API are 28-day rolling. Same source, different aggregation windows — numbers won't match exactly.
• "CrUX captures every Chrome user." Only opted-in users with sync enabled, no custom passphrase, and history reporting on. Estimates put CrUX coverage at single-digit percentages of total Chrome traffic — large enough to be statistically meaningful, not large enough to show every URL.