Google's field-data metrics for loading, interactivity and visual stability.
Core Web Vitals are three metrics Google uses to measure real-world page experience: Largest Contentful Paint (LCP), Interaction to Next Paint (INP) and Cumulative Layout Shift (CLS). LCP tracks how quickly the main content renders, INP measures how responsive the page feels across all interactions, and CLS measures how much the layout jumps around while loading.
They are a lightweight ranking signal, but their bigger value is as a shared, measurable definition of a fast, stable page. The scores that matter come from field data (real Chrome users in the CrUX dataset), not lab tools like Lighthouse, which only approximate them.
Each metric has a good/needs-improvement/poor threshold, assessed at the 75th percentile of your real users. A page passes only if all three are in the good range.
The most common error is optimising for the Lighthouse lab score and ignoring the field data in Search Console, which is what Google actually uses. INP problems are usually caused by heavy JavaScript blocking the main thread on interaction, and CLS is usually images or ads without reserved space, or fonts that reflow text.
Common questions
Straight answers on how this fits your marketing and build.
Yes, but as a minor tie-breaker within the page-experience signals. They rarely outweigh relevance and links, but a poor experience can cost you when competitors are otherwise equal.
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