Definition
Core Web Vitals are three real-world page-experience metrics, LCP, INP and CLS, that Google uses as ranking signals within its Page Experience system. LCP (Largest Contentful Paint) measures how long until the main content renders, with a target under 2.5 seconds; INP (Interaction to Next Paint) measures how quickly the page responds to clicks, taps and key presses, targeting under 200 milliseconds; CLS (Cumulative Layout Shift) measures how much visible elements move as the page loads, targeting a score under 0.1. Together they capture load speed, responsiveness and visual stability rather than lab benchmarks alone. Google collects the data from actual Chrome users, reports it at the 75th percentile over a rolling 28-day window in Search Console and the Chrome User Experience Report (CrUX), and treats them as a tie-breaker signal: they mainly affect rankings when pages are otherwise similarly relevant, so strong content can still outrank a technically faster page that answers the query less well.
How it works
Each Core Web Vital is measured at the 75th percentile of real visitors over a 28-day window. A site passes the assessment when all three metrics are in the "good" range for at least 75% of page views. Google publishes the data per origin and per URL group in Search Console.
Why it matters
Failing Core Web Vitals depresses rankings for competitive queries and signals a slow or jarring user experience. Improving them usually means optimising images, eliminating render-blocking scripts, fixing layout-shifting elements, and lowering server response times. A good host with a CDN does much of this for you.