Google uses Core Web Vitals as ranking signals. A site scoring 90+ on PageSpeed Insights gains a measurable ranking advantage over slower competitors — especially on mobile. A 1-second delay in page load reduces conversions by 7%.
The Three Core Web Vitals
Core Web Vitals thresholds
| Metric | What It Measures | Good | Poor |
|---|---|---|---|
| LCP | Loading — when main content loads | < 2.5s | > 4.0s |
| INP | Responsiveness — response to clicks | < 200ms | > 500ms |
| CLS | Visual stability — layout shifts | < 0.1 | > 0.25 |
Fixing LCP
- Preload the LCP element with <link rel="preload">
- Serve images in WebP or AVIF format (30-50% smaller than JPEG)
- Use a CDN — server proximity reduces TTFB dramatically
- Defer non-critical JavaScript
- Enable HTTP/2 or HTTP/3 on your server
Next.js-Specific Optimisations
- Use next/image for automatic WebP, lazy loading, and size optimisation
- Use next/font to eliminate CLS from custom fonts
- Enable App Router with React Server Components to reduce JS bundle size
- ISR for data-heavy pages to reduce cold load times
🛠️
Tooling
Test with Chrome DevTools > Performance > Web Vitals AND real-user data in Search Console > Core Web Vitals. Lab scores and field data can differ significantly — optimise for field data.
Core Web VitalsPageSpeedPerformanceSEOTechnical SEO
Tanvir Tuhin
AI consultant, digital marketer, and study abroad mentor based in Aberdeen, UK. Founder of JJAT Education.
Work with Tanvir