Core Web Vitals

What it means

Core Web Vitals (CWV) are the three real-user-experience metrics Google uses to assess page performance as a ranking factor. They measure loading speed, interactivity, and visual stability — the three dimensions of perceived performance from a user's perspective.

Largest Contentful Paint (LCP) measures how long the largest visible element takes to render. Interaction to Next Paint (INP) — which replaced First Input Delay in 2024 — measures the worst input delay a user experiences during their visit. Cumulative Layout Shift (CLS) measures how much the page layout shifts unexpectedly while loading.

Google grades each metric as Good, Needs Improvement, or Poor based on the 75th-percentile real-user value (the worst experience 25% of users had). The data comes from the Chrome User Experience Report (CrUX), aggregating real Chrome sessions — not synthetic Lighthouse audits.

Key takeaways

• LCP target: under 2.5 seconds
• INP target: under 200 milliseconds
• CLS target: under 0.1
• Real-user data (CrUX), not synthetic Lighthouse scores, is what Google ranks on
• CWV is a confirmed but lightweight ranking factor — important but rarely the difference between rank 1 and rank 20

When it matters

CWV matters most when you fail one of the three metrics on a high-traffic template. A site-wide CLS issue on every product page is a five-figure-traffic problem. Borderline CWV scores on low-traffic pages rarely move the needle.