What the data says
Google uses Core Web Vitalsas a ranking signal. Studies from Deloitte and Google consistently show clear correlations: a 0.1-second reduction in load time increases mobile conversion by 8–10% in retail. In B2B, the impact shows up mostly in bounce rate: users who wait > 3 seconds leave twice as often as those who see the page under 1 second.
The three metrics that matter
- LCP (Largest Contentful Paint) — how long until the main element appears. Target: under 2.5 seconds.
- INP (Interaction to Next Paint) — how quickly the UI responds to click/tap. Target: under 200 ms.
- CLS (Cumulative Layout Shift)— how much content "jumps" during load. Target: under 0.1.
Where the losses come from
In 80% of cases, the culprits are the same: unoptimized images, third-party scripts loaded synchronously (GA, pixels, chat widgets), render-blocking fonts, and a server with no caching. Rarely the "tech stack" — almost always the configuration.
What to do, concretely
- Images through
next/imageor equivalent, with explicitwidth/height. - Analytics and chat scripts load only after consent (and always with
async/defer). - Self-hosted fonts or loaded with
display: swap. - HTTP/2 or HTTP/3 + Brotli/Gzip at the proxy level (NGINX, Cloudflare).
- Cache on static assets (1 year, immutable) and on HTML (short, but existent).
Conclusion
A fast website is not a technical luxury, it's a sales tool. If you don't measure Core Web Vitals monthly, you don't know how much money you're losing. PageSpeed Insights is free and takes a minute — a good starting point.