Core Web Vitals (CWV) are the three Google metrics that measure real user experience on your site. Since March 2024, INP replaced FID as the interactivity metric. Here is what matters in 2026.
The three metrics and thresholds
| Metric | Measures | Good | Needs work | Poor |
|---|---|---|---|---|
| LCP | Time until largest viewport element renders | ≤ 2.5 s | 2.5–4 s | > 4 s |
| INP | Time to respond to any interaction | ≤ 200 ms | 200–500 ms | > 500 ms |
| CLS | How much the page shifts during load | ≤ 0.1 | 0.1–0.25 | > 0.25 |
To pass Google's review and count as "Good CWV", all three must be in the green band for 75% of visits.
What changed in 2024
INP replaced FID
FID measured only the delay before the first user action. INP measures every interaction, not just the first. Slow menus, modals and JS handlers now hit rankings directly.
Stricter mobile focus
Google relies on CrUX mobile data. A site that's fast on desktop but slow on mobile loses ranking.
How to measure CWV
- PageSpeed Insights at
pagespeed.web.dev. - Google Search Console → Core Web Vitals.
- Chrome DevTools + Web Vitals extension.
- web-vitals JS library for real visitor data.
Common LCP issues
- Slow server response (TTFB > 600 ms).
- Heavy unoptimised images — WebP/AVIF,
fetchpriority="high"on hero. - Render-blocking CSS/JS.
- Custom fonts without
font-display: swap.
Common INP issues
- Heavy event handlers blocking main thread.
- React/Vue components with heavy re-renders.
- Third-party scripts — lazy-load.
- Large DOM (> 1,500 nodes).
Common CLS issues
- Images without dimensions.
- Embeds without reserved space.
- Late-injected ads.
- Custom font swap.
Quick WordPress checklist
- Object cache (Redis or Memcached).
- Full-page cache plugin (WP Rocket, FlyingPress).
- WebP image conversion.
- Disable unused plugins.
- PHP 8.3 or 8.4 — 15–25% faster than 8.0.
- Consider a CDN (Cloudflare, Bunny).
Want an audit? SEO + maintenance includes monthly CWV monitoring. Get a quote.
