The three metrics and their targets
| Metric | What it measures | Good score |
|---|---|---|
| Largest Contentful Paint (LCP) | How fast the main content appears | 2.5 seconds or less |
| Interaction to Next Paint (INP) | How fast the page reacts to taps and clicks | 200 milliseconds or less |
| Cumulative Layout Shift (CLS) | How much the layout jumps while loading | 0.1 or less |
Google judges each metric at the 75th percentile of real visits, separately for phones and desktops. INP replaced First Input Delay as a Core Web Vital in 2024.
How much they affect rankings
Google says its ranking systems use Core Web Vitals. It also says it shows the most relevant content even when page experience is weak. Think of the vitals as a tiebreaker between pages that answer a search equally well. They matter more for conversions than for positions.
What usually breaks each one
- LCP. Huge hero images, slow hosting and render-blocking scripts.
- INP. Heavy page builders, chat widgets and tracking scripts.
- CLS. Images without set sizes, late banners and web fonts that swap.
Field data vs lab data
PageSpeed Insights shows two kinds of numbers. Field data comes from real Chrome users and is what Google uses. Lab data is a single test run that helps you find the cause. A new or low-traffic page may have no field data yet, so the lab score is your only guide until visits build up.
Search Console groups your URLs into good, needs improvement and poor in its Core Web Vitals report. Fix the templates behind the poor groups first, since one template fix repairs many pages at once.
Speed has a wider effect on leads, covered in how site speed affects SEO. We build every web design project to pass all three metrics on phones.