Google
A Google initiative defining a set of real-world, user-centered metrics—Largest Contentful Paint (LCP), First Input Delay (FID), and Cumulative Layout Shift (CLS)—used to measure and report page experience quality.

SEMRush
A Site Audit metric set measuring loading performance (LCP), visual stability (CLS), and interactivity (TBT as a lab proxy for FID), helping identify and fix user experience issues on a website.