Core Web Vitals
Core Web Vitals are Google's three page experience metrics: Largest Contentful Paint for loading speed, Interaction to Next Paint for responsiveness, and Cumulative Layout Shift for visual stability. They are measured from real Chrome users in the field, not from laboratory tests.
Why it matters for your rankings
Core Web Vitals are a confirmed ranking signal, though a modest one. They rarely outweigh relevance, so a fast page about the wrong topic still loses to a slow page about the right one.
Their real value is commercial. These metrics measure friction that costs conversions directly. Pages that load slowly or shift under the reader's finger lose people who would otherwise have bought, and that revenue loss is usually larger than the ranking effect. They also function as a tiebreaker in competitive results where several pages are equally relevant. The critical detail is that scores come from field data collected from actual visitors over 28 days, so improvements take weeks to appear no matter how good your lab results look.
How to check it on your site
Read field data first
In Search Console open the Core Web Vitals report. This is the CrUX field data Google actually uses, unlike a one-off Lighthouse run.
Diagnose per template
Group failing URLs by page type. One bad template usually explains most failures, which makes the fix a single job.
Attack the largest element
Run PageSpeed Insights, note the LCP element, then compress it, serve modern formats and preload it.
Reserve space to stop shift
Set explicit width and height on images and embeds, and reserve height for banners and ads, to eliminate most CLS.