Searchlab PageSpeed and Core Web Vitals, Explained Simply
Google ranks fast pages higher. Real users abandon slow ones. PageSpeed Insights measures both, what the lab tests AND what your actual visitors experience.
The 3 Core Web Vitals you must pass
- LCP, Largest Contentful Paint. When the biggest visible element loads. Pass: under 2.5 seconds.
- INP, Interaction to Next Paint. How fast your page reacts when clicked or tapped. Pass: under 200 milliseconds.
- CLS, Cumulative Layout Shift. How much things jump around as the page loads. Pass: under 0.1.
Most common speed killers and the fix
- Giant hero images. Compress to WebP under 200 KB. Lazy-load anything below the fold.
- Third-party scripts. Analytics, chat widgets, ads. Add
deferor load on user interaction only. - Render-blocking CSS. Inline critical CSS for above-the-fold content. Defer the rest.
- Web fonts. Use
font-display: swapand preload only the weights you actually need. - No CDN. Static assets should be served from edge locations close to your visitors.
Mobile vs desktop: Google now ranks based on mobile performance. Always optimise for the mobile score first, even if your audience is desktop-heavy.
Lab data vs field data
PageSpeed shows two sets of numbers. Lab data is a simulated test in a clean environment, useful for debugging. Field data (when available) is real-user measurements from Chrome. Field data is what Google actually ranks on, so prioritise improving those numbers.
Frequently asked
Why is my mobile score worse than desktop?
Mobile devices have weaker CPUs and slower networks. The same scripts and images that load fast on a laptop choke a phone. Test on a 4G connection at minimum.
How often should I check?
Every code deploy if you change layout, scripts, or images. Otherwise weekly. Speed regresses easily as new features land.
Are 100 scores possible?
Yes, but rare on real production sites with ads, analytics, and CMS templates. 85+ on mobile is realistic and great.