What is the Chrome UX Report (CrUX)?

Chrome UX Report (CrUX), explained

Chrome's documentation calls CrUX the official dataset of the Web Vitals program. It collects metrics from Chrome users who have opted in, across real devices and networks, and reports them over a rolling 28-day window. It covers the Core Web Vitals (LCP, INP, CLS) and other metrics like FCP and TTFB, split by device type.

Not every site is included. Pages and origins must be publicly discoverable and sufficiently popular to produce a statistically meaningful sample. New or low-traffic sites often have no CrUX data at all, which is why PageSpeed Insights sometimes shows only lab results and Search Console's Core Web Vitals report can be empty.

You can reach the data in several ways: PageSpeed Insights for a single URL or origin, Search Console's Core Web Vitals report grouped by similar URLs, the CrUX API with daily updates, CrUX Vis for trends, and a public BigQuery dataset updated monthly. Chrome's documentation also notes that Google Search uses CrUX data in its page experience evaluation.

Because it's a 28-day rolling window, fixes take weeks to show. Ship a speed fix today and the field numbers move gradually as old page loads age out. If you need faster feedback, add your own real-user monitoring with a library like web-vitals and send the values to your analytics.

Why it matters for founders

CrUX, not your Lighthouse score, is what Google sees for Core Web Vitals. Knowing it lags by weeks and needs traffic explains why your reports don't change the day you ship.

Example

You fix a layout shift on your pricing page. PSI's lab data improves immediately, but the CrUX field value takes about four weeks to drop below 0.1 as older visits roll out of the window.

Common mistakes

• Expecting field data to change the day you deploy.
• Assuming a new site will have CrUX data.
• Confusing lab scores with field data.
• Not adding your own real-user monitoring for faster feedback.