Core Web Vitals are three metrics Google uses to measure the real-world experience of your store. They feed into rankings, and — more importantly — they track things shoppers actually feel. Here's each one in plain English, with the fixes that work on Shopify.
The three metrics
| Metric | Measures | Good | Poor |
|---|---|---|---|
| LCP | How fast the main content loads | ≤ 2.5s | > 4s |
| INP | How fast the page responds to taps | ≤ 200ms | > 500ms |
| CLS | How much the layout jumps around | ≤ 0.1 | > 0.25 |
LCP — Largest Contentful Paint
This is usually your hero image or main heading. To improve it:
- Prioritise (preload) the hero image, and don't lazy-load it
- Serve it as a correctly sized WebP
- Cut render-blocking CSS and JavaScript
- Preconnect to critical third-party domains
INP — Interaction to Next Paint
INP measures how quickly the page reacts when someone taps or clicks. Heavy JavaScript is the usual culprit — it keeps the main thread busy so taps feel laggy. To improve it:
- Reduce and defer JavaScript (fewer apps, leaner theme)
- Break up long-running scripts
- Remove unused third-party widgets
CLS — Cumulative Layout Shift
CLS is the annoying jump when content loads and pushes everything down. To fix it:
- Set width/height (or aspect ratio) on all images and embeds
- Reserve space for banners, ads, and app content
- Preload fonts and use `font-display: swap` to avoid text reflow
Measure with field data, not just lab scores
A Lighthouse score is a lab test on one device. Google actually ranks on field data — real visits from the CrUX report and Search Console's Core Web Vitals report. Check those, because a great lab score can still hide a poor real-world experience (and vice versa).
Where most Shopify stores lose points
In practice it's images (LCP), too many apps/scripts (INP), and missing image dimensions (CLS). Fix those three and most stores move into the green.
Want us to get your store passing all three? We run a free Core Web Vitals audit for brands in Nairobi and hand you the specific fixes.