What it means
Core Web Vitals are three specific metrics Google uses to evaluate the user experience of a webpage:
- Largest Contentful Paint (LCP) - how long it takes for the main content to appear. Target: under 2.5 seconds
- Interaction to Next Paint (INP) - how quickly the page responds to user input. Target: under 200 milliseconds
- Cumulative Layout Shift (CLS) - how much visible content shifts unexpectedly during loading. Target: under 0.1
INP replaced First Input Delay (FID) as the responsiveness metric in March 2024.
Why it matters
Google uses Core Web Vitals as a ranking signal under its Page Experience system. The signal is most influential in tie-breaker situations - between two pages of similar relevance, the faster, more stable one wins.
Beyond rankings, Core Web Vitals affect conversion rates directly. Slow, janky pages bounce. Studies repeatedly show that improvements in LCP and INP correlate with measurable lifts in form submissions and revenue.
How it's used
To improve Core Web Vitals:
- LCP - optimize images, use modern formats (WebP, AVIF), preload critical resources, reduce render-blocking JavaScript
- INP - break up long JavaScript tasks, defer non-critical scripts, minimize main-thread work
- CLS - reserve space for images and embeds, avoid late-injected ads, use stable font loading
Measure with PageSpeed Insights and the Web Vitals report in Search Console. Field data (real users) matters more than lab data for ranking purposes.