Core Web Vitals
Google’s three user-experience metrics: LCP, INP, and CLS.
Core Web Vitals summarize real-user experience: loading (Largest Contentful Paint), interactivity (Interaction to Next Paint), and visual stability (Cumulative Layout Shift). They are measured from the Chrome User Experience Report field data, not just lab Lighthouse runs, though lab tools approximate them.
Why developers care
Google has confirmed Core Web Vitals as ranking factors alongside page experience signals. Poor scores correlate with higher bounce and lower conversion even without SEO. The upside: many fixes are server and asset configuration—compression, cache lifetimes, image dimensions—not months of React refactor.
Example
Good targets (field data, mobile):
LCP < 2.5 s
INP < 200 ms
CLS < 0.1