Core Web Vitals
Core Web Vitals are Google’s three field metrics for page experience: Largest Contentful Paint (LCP) for loading speed, Interaction to Next Paint (INP) for responsiveness, and Cumulative Layout Shift (CLS) for visual stability, each measured on real user visits.
Each metric targets a different felt problem. LCP measures how long the main content takes to render, INP measures how quickly the page responds to taps and clicks across the whole visit, and CLS measures how much the layout jumps around as things load. Google publishes target thresholds (for example LCP under 2.5 seconds and CLS under 0.1) and uses field data from real Chrome users, not lab tests, to decide whether a page passes.
Core Web Vitals are a confirmed ranking signal, but a modest one: they act mainly as a tie-breaker between pages of similar relevance, so a fast page with weak content will not outrank a slow page that answers the query better. The honest framing is that good vitals protect rankings and conversion rather than win them outright.
Third-party widgets are a frequent CLS offender. A review block, star rating, or testimonial carousel that loads after the first paint and then pushes existing content down adds layout shift exactly where shoppers are reading. Reserving space for the widget ahead of time, or rendering ratings server-side, keeps CLS low without giving up the social proof.