Core Web Vitals are Google's way of measuring whether a page actually feels fast to a real visitor, not just fast in a lab test. Three metrics matter most: Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS).
Largest Contentful Paint (LCP)
LCP measures how long it takes for the largest visible element (usually a hero image or heading) to render. Anything under 2.0 seconds is considered good. The biggest wins here almost always come from image optimization and prioritizing the hero asset for early load.
Interaction to Next Paint (INP)
INP measures how responsive a page feels when someone clicks, taps, or types. Heavy JavaScript execution on the main thread is the usual culprit. Breaking up long tasks and deferring non-critical scripts is the most reliable fix.
Cumulative Layout Shift (CLS)
CLS measures visual stability: how much content jumps around as a page loads. Reserving space for images and ads before they load, and avoiding content injected above existing content, eliminates most CLS issues.