Largest Contentful Paint
Good: ≤ 2,5 s
Time to render the largest element visible in the viewport. Usually a hero image or a heading block.
Core Web Vitals
Three metrics Google treats as a page-experience signal. We measure them locally and say plainly how they differ from real-user data.
Cumulative Layout Shift
Good: ≤ 0,1
The sum of unexpected layout shifts. The most common cause: images and ads without reserved dimensions.
Interaction to Next Paint
Good: ≤ 200 ms
Responsiveness to interaction. In lab conditions TBT — total blocking time of the main thread — approximates it.
Lab data versus field data
Lighthouse measures in a controlled environment and is repeatable — good for diagnosis. The Core Web Vitals Google actually uses come from CrUX, that is real Chrome users over 28 days. This is why our score can differ from PageSpeed Insights, and that is expected rather than a fault.