Core Web Vitals are three metrics Google uses to measure user experience: LCP (loading), CLS (stability), and INP (interactivity). Since 2021 they are official ranking factors. On an e-commerce site loaded with product images and marketing scripts, they often represent the largest untapped SEO improvement opportunity.
The three Core Web Vitals explained
LCP — Largest Contentful Paint
Time until the largest visible element loads (usually the hero image on a product page). Target: under 2.5s. Fix: compress images (WebP), preload the hero image, use Shopify's CDN.
CLS — Cumulative Layout Shift
Amount of unexpected layout movement after initial load. Target: under 0.1. Fix: always set width + height attributes on images and video elements. Reserve space for lazy-loaded content.
INP — Interaction to Next Paint
Time between user interaction and next visual update. Target: under 200ms. Fix: defer non-critical JavaScript, avoid long main-thread tasks from Shopify apps.
| Metric | Good | Needs improvement | Poor |
|---|---|---|---|
| LCP | Under 2.5s | 2.5 to 4s | Over 4s |
| CLS | Under 0.1 | 0.1 to 0.25 | Over 0.25 |
| INP | Under 200ms | 200 to 500ms | Over 500ms |
Measure your Core Web Vitals in Google Search Console (Experience > Core Web Vitals) — this shows field data (real users) rather than lab data. Lab data from PageSpeed Insights can look good while real-user data is poor due to third-party scripts loading after tests.
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FAQ
They are a tiebreaker at similar quality levels — not a dominant signal like title tags or backlinks. But on competitive keywords where many pages have similar on-page SEO, Core Web Vitals can make a difference. More directly: a slow site loses conversions independently of SEO.