Website speed affects more than technical scores. It determines how quickly users see the main content, whether they can interact with the page without delay, and whether the interface shifts while loading.
What Exactly to Measure
To assess real user experience, Google uses Core Web Vitals: LCP for how quickly the main content appears, INP for interface responsiveness, and CLS for visual stability. “Good” thresholds are LCP up to 2.5 s, INP up to 200 ms, and CLS up to 0.1.
How Speed Is Connected to Business
A slow page adds friction at every step: users wait longer for the hero section, see the CTA later, may click a button repeatedly, or leave before the form becomes available. The impact on conversion depends on the audience, devices, and the product itself, so there is no universal growth percentage.
What to Optimize First
- compress images and serve them at the correct dimensions;
- do not load below-the-fold images until they are needed;
- reduce render-blocking CSS and JavaScript;
- set media dimensions to avoid layout shifts;
- cache static resources and use a CDN when justified;
- review third-party scripts — analytics and widgets often create significant load.
Lab and Field Data
Lighthouse is useful for diagnostics, but real-user data in Search Console or the Chrome UX Report also matters when setting priorities. Optimize the problems that actually harm the experience, not a “100 score.”