The three metrics
LCP — Largest Contentful Paint. How long until the largest visible element (usually a hero image or headline block) finishes rendering. Good: ≤ 2.5s. This is the metric third-party scripts and heavy images hurt most.
INP — Interaction to Next Paint. How long between a user interaction (tap, click, key press) and the next visual update. Good: ≤ 200ms. INP replaced First Input Delay (FID) as a Core Web Vital in March 2024, and it is stricter — it looks at all interactions across the page's lifetime, not just the first.
CLS — Cumulative Layout Shift. How much visible content unexpectedly moves during the page's lifetime. Good: ≤ 0.1. Late-loading widgets, images without dimensions, and injected banners are the classic causes. See cumulative layout shift for the deep dive.
Field data, not lab data
Core Web Vitals are assessed from the Chrome User Experience Report (CrUX) — anonymized field data from real Chrome users — at the 75th percentile. A page passes a metric when at least 75% of real visits hit the "good" threshold. Lab tools like Lighthouse simulate a run on emulated hardware and are useful for debugging, but the assessment that matters is the field data.
Why it matters for ecommerce
Page experience is a Google ranking consideration, but the more direct effect is on conversion: slow LCP and janky INP lose visitors before the product page finishes loading. The practical playbook for passing while running a chat widget and animations lives in the ecommerce site speed guide, and you can check any page's current field data with the page speed analyzer.
Related terms
- Cumulative Layout Shift — the visual-stability vital in detail
- Conversion rate — the business metric speed feeds
Last updated July 6, 2026.