Core Web Vitals are a set of metrics with which Google measures a web page's real user experience: how fast the main content loads (LCP), how smoothly the page responds to input (INP) and how stable the layout stays while loading (CLS). They are part of the Page Experience ranking signal — poor values cost visibility and conversion.
LCP (Largest Contentful Paint): load time of the largest visible element, good under 2.5 seconds. INP (Interaction to Next Paint): response time to user input, good under 200 milliseconds. CLS (Cumulative Layout Shift): visual stability, good under 0.1.
Together the three describe how a page feels to real users: quick to appear, instantly usable and free of jumping elements.
Google uses Core Web Vitals as a ranking factor and measures them on real user data (field data from the Chrome UX Report). Relevance beats speed, but on comparable content good vitals tip the balance.
More importantly: slow, jumping pages cause drop-offs. Poor vitals cost twice — in ranking and in revenue.
Optimize images and serve them in modern formats (AVIF/WebP), reduce critical CSS and JavaScript, lower server and cache response times. Avoid layout shifts by setting fixed dimensions for images and embeds.
Measure with PageSpeed Insights, Lighthouse or Google Search Console. Lab tools help with debugging, but the field data of real visitors is what gets scored.
In March 2024 INP replaced FID (First Input Delay) as a Core Web Vital. INP measures responsiveness across the whole session, not just the first interaction — a stricter standard.
They are a confirmed but moderate factor. Relevance beats speed; on comparable content good vitals tip the balance — and they always improve conversion.
Google scores field data from real users. Lab tools like Lighthouse help with debugging but don't replace the field data in Search Console.