What Are Core Web Vitals?
Google uses three specific performance metrics to measure how users experience your website. Understanding them tells you exactly what to improve to satisfy both Google and your visitors.
Core Web Vitals are three Google metrics measuring page experience: LCP (how fast the main content loads, target under 2.5s), INP (how quickly the page responds to interactions, target under 200ms) and CLS (whether the page shifts around during loading, target under 0.1). All three are confirmed ranking factors.
The Three Core Web Vitals Explained
| Metric | What It Measures | Good | Needs Work | Poor |
|---|---|---|---|---|
| LCP (Largest Contentful Paint) | How long the main visible content takes to load | Under 2.5s | 2.5s to 4.0s | Over 4.0s |
| INP (Interaction to Next Paint) | How quickly the page responds to clicks, taps and keyboard input | Under 200ms | 200ms to 500ms | Over 500ms |
| CLS (Cumulative Layout Shift) | How much page elements move around unexpectedly during loading | Under 0.1 | 0.1 to 0.25 | Over 0.25 |
Usually caused by large unoptimised images, slow server response times or render-blocking JavaScript. Fix with image compression, CDN and lazy loading.
Caused by heavy JavaScript execution on interaction. Fix by reducing JS bundle size, deferring non-critical scripts and optimising event handlers.
Caused by images without specified dimensions, ads loading late or dynamically injected content. Fix with explicit width/height on media elements.
How to Check Your Core Web Vitals
- Google Search Console Core Web Vitals report shows field data from real users visiting your site, broken down by URL group.
- PageSpeed Insights (pagespeed.web.dev) provides both lab and field data with specific diagnostics for each metric.
- Chrome DevTools Lighthouse tab gives a detailed performance audit for local testing.
- Google Search Console Coverage report flags URLs with poor Core Web Vitals at scale.
PageSpeed Insights shows two types of data. Lab data is measured in a controlled environment. Field data reflects real user experiences on your actual visitors devices and connections. Google uses field data for ranking. A good lab score does not guarantee good field data, particularly if your visitors predominantly use slower mobile connections.
Do Core Web Vitals Directly Cause Ranking Changes?
Core Web Vitals are one of many ranking signals, not a dominant one in isolation. A page with poor Core Web Vitals will not instantly drop because of them. However, when content quality and authority are comparable between competing pages, Core Web Vitals become a tiebreaker. And in competitive niches, tiebreakers matter.
More importantly, poor Core Web Vitals directly damage conversion rates. Slower loading time means higher bounce rates, fewer pages viewed and lower conversion percentages, regardless of whether they affect rankings.
Costs You Clicks Every Day.
Every second your page takes to load reduces conversions. Every failed Core Web Vital is a competitive disadvantage. A technical fix now pays back for years. Book a free call and find out where you stand.