Core Web Vitals Assessment showing LCP 10.6s while google pagespeed report showing LCP 3.5s why?
You can see the similar test result on Google PageSpeed Insights.
The header heading Core web Vitals Assessment LCP is 10.6 seconds but the bottom report shows LCP 3.5 seconds.
The difference between Core Web Vitals (LCP) and Google PageSpeed reports (LCP) depends on many factors. here are some of them:
The Core Web Vitals:
The Core Web Vitals metrics score represents the real actual user's experience.It also depends on users' conditions, device, location and network conditions.
So the LCP is showing different users.
The Google PageSpeed Insights:
Actually it generates metrics tests from a self defined environment.So it does not get the data of real world end users for ex: device hardware, poor device network, what software extension installed in device or network speeds. It is also same for other metrics for ex: First Contentful Paint (FCP), Time to First Byte (TTFB), Cumulative Layout Shift (CLS) and Interaction to Next Paint (INP)