SEO

CrUX (Chrome User Experience Report)

Q: What is CrUX?

CrUX (Chrome User Experience Report) is Google's public database of real user performance data. Chrome users who permit the transmission supply anonymised LCP, INP and CLS values. It forms the basis for Core Web Vitals as a ranking signal.

Q: What is the difference from Lighthouse values?

CrUX is field data, Lighthouse is lab data. Field: real users under real network conditions. Lab: a simulated browser with standardised conditions. What is relevant to Google rankings is the CrUX field value, not the Lighthouse lab value.

Q: How does Google know what values my site has?

From CrUX per origin. Google aggregates values per domain over 28-day windows. Sites below the traffic threshold (around 100 users/month) have no CrUX data — Google then uses lab values or fallback assessments.

Q: Where can CrUX values be seen?

In Google Search Console under ”Core Web Vitals" for each site. Also in PageSpeed Insights in the ”Field" section. Publicly accessible via the Chrome UX Report API and BigQuery public datasets.

Also known as: CrUX, Chrome User Experience Report, Field data

The Chrome User Experience Report (CrUX) is Google's public dataset, which collects real user data on the performance of millions of websites. The data comes from Chrome users who take part voluntarily and is aggregated at URL or origin level using a 28-day median. CrUX is the field data source for Core Web Vitals — and it is precisely this field data that is relevant to rankings, not the synthetic lab data from Lighthouse. For SEO, CrUX is therefore the most important page speed data source.

Where CrUX data can be accessed

PageSpeed Insights — shows CrUX data alongside Lighthouse lab data.
Google Search Console — the Core Web Vitals report is based on CrUX.
CrUX BigQuery dataset — for in-depth analyses across large sets of URLs.
CrUX API — programmatic access for tools and dashboards.
CrUX Dashboard on Looker Studio — ready-made visualisations.

CrUX limitations

Sample size — small websites often have too little Chrome traffic for CrUX data. ”Not enough data" is a frequent response.
Chrome only — Safari, Firefox and Edge users are missing.
28-day median — performance improvements only become visible after a delay.
Aggregate values — diagnosis of an individual session is not possible.
Opt-in only — Chrome users must have given their consent to analytics.

Reading CrUX data correctly

The key metric is the 75th percentile — 75 % of users have a value equal to or better than this. What counts for ranking relevance is: is the 75th percentile of LCP below 2.5 s? Is the 75th percentile of INP below 200 ms? Is the 75th percentile of CLS below 0.1? Only then does a page count as ”Good". Lab data from Lighthouse may show ”95/100" while the CrUX field data paints a markedly different picture — for instance when real users are browsing on slow mobile connections.

Example from practice

Example: A SaaS domain had a Lighthouse performance score of 92 — excellent at first glance. The CrUX data, however, showed an LCP at the 75th percentile of 3.8 s (poor) and an INP of 280 ms (needs improvement). The explanation: Lighthouse runs on a simulated 4G connection, whereas real mobile users (often on slower connections and weaker devices) have a considerably worse experience. Optimisation focused on real worst-case scenarios (compressing images even more aggressively, splitting the JS bundle): after 8 weeks, CrUX LCP was down to 2.1 s and INP to 180 ms — both ”Good". The visibility of the top pages rose by 12 % over the same period.

Frequently asked questions

What is CrUX?

CrUX (Chrome User Experience Report) is Google's public database of real user performance data. Chrome users who permit the transmission supply anonymised LCP, INP and CLS values. It forms the basis for Core Web Vitals as a ranking signal.

What is the difference from Lighthouse values?

CrUX is field data, Lighthouse is lab data. Field: real users under real network conditions. Lab: a simulated browser with standardised conditions. What is relevant to Google rankings is the CrUX field value, not the Lighthouse lab value.

How does Google know what values my site has?

From CrUX per origin. Google aggregates values per domain over 28-day windows. Sites below the traffic threshold (around 100 users/month) have no CrUX data — Google then uses lab values or fallback assessments.

Where can CrUX values be seen?

In Google Search Console under ”Core Web Vitals" for each site. Also in PageSpeed Insights in the ”Field" section. Publicly accessible via the Chrome UX Report API and BigQuery public datasets.

Used in Rankmio for

Core Web Vitals audit with CrUX data

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Last updated: 2026-06-17 · Browse all glossary entries