LCP, largest contentful paint, measures when the main content is visible; the target is 2.5 seconds or less. INP, interaction to next paint, replaced FID in March 2024 and measures how fast the page reacts to a tap or a click; the target is 200 milliseconds or less. CLS, cumulative layout shift, measures how much the layout jumps while loading; the target is 0.1 or less. The thresholds apply to the slowest quarter of visits.
The data comes from Chrome users, so a page needs traffic to have a score. The usual culprits are heavy images, scripts that block rendering, and content inserted after load. Fixing them rarely changes rankings by itself, but a slow page loses visitors before any ranking matters.