Why does Search Console show Core Web Vitals problems that PageSpeed does not?

Search Console and PageSpeed Insights measure different things: the Core Web Vitals report uses real user data from the Chrome UX Report (CrUX) over the last 28 days, while the PageSpeed score comes from a single simulated Lighthouse test. A good lab score therefore says little about how real visitors experienced your pages. In addition, Search Console rates groups of similar URLs, not the single page you tested.

Neither tool is wrong. The field data shows what users experienced; the lab test helps you find the cause. For Core Web Vitals in Search, the field data counts.

Why do the two tools show different results?

• Field data versus lab data. CrUX collects anonymised measurements from real Chrome users on many devices and connections. Lighthouse loads the page once under fixed conditions, simulating a mid-range mobile device for the mobile test.
• 28 days versus now. Search Console and the field data in PageSpeed Insights cover a trailing 28-day period. A fix you deployed yesterday shows up in the lab test immediately but only gradually in the field data.
• URL groups instead of single URLs. Search Console groups similar pages. A group gets the status of its worst metric. A slow template, such as product pages with large images, can mark the whole group as “Poor”, even if the URL you tested looks fine.
• INP has no lab value. Interaction to Next Paint needs real user interactions. Lighthouse cannot measure it directly, so a good lab score can coexist with poor INP in the field.
• The 75th percentile. Field values are judged at the 75th percentile. If a quarter of your visitors are on slow devices or connections, that shows in the field data but not in a single lab run.

Which data should I trust?

For the question “Do my pages pass Core Web Vitals?”, rely on the field data: the Core Web Vitals report in Search Console and the upper section in PageSpeed Insights that shows real user data. The Lighthouse score below it is a diagnostic aid, not an assessment of user experience. If PageSpeed Insights shows no field data for a URL, there is not enough CrUX data for that page; it may then fall back to origin-level data.

How do I close the gap?

1. Find the affected metric. In the Core Web Vitals report, open mobile or desktop and check whether LCP, INP or CLS is the problem.
2. Test sample URLs. Click an issue and use the example URLs of the URL group. Run them through PageSpeed Insights and compare the field data at the top with Search Console.
3. Use the lab test for the cause. The diagnostics in Lighthouse show, for example, which element is the LCP element or which elements shift the layout. For INP, look at long JavaScript tasks and test interactions with real clicks in Chrome DevTools.
4. Fix the template, not the single page. Because Search Console evaluates groups, changes to the shared template usually have the biggest effect.
5. Start validation. After the fix, click Start tracking on the issue in Search Console. Google then monitors the field data for 28 days before considering the issue fixed.

To shrink large images and convert them to WebP, you can use our image optimizer.

Use Search Console to see where real users have problems and PageSpeed Insights to find out why. Judge success by the field data after 28 days, not by the lab score.

Sources

• Search Console Help: Core Web Vitals report
• Google for Developers: About PageSpeed Insights
• web.dev: Why lab and field data can be different
• Google Search Central: Core Web Vitals and Google Search results

Want to know why your pages fail Core Web Vitals despite a good PageSpeed score? We analyse field data, templates and scripts and show you which changes help real users. Book a free intro call or read more about our search engine optimisation.