Optimizing Core Web Vitals for business websites
The three metrics that decide UX and SEO ranking — and how we push Lighthouse past 95.
Users leave within the first three seconds if a page is slow. Google knows it, and since 2021 has made Core Web Vitals a ranking factor. For a business website, speed is no longer a technical detail — it is revenue.
The three metrics to know by heart
LCP measures when the largest element appears. INP measures input latency. CLS measures layout shift. A good page needs LCP under 2.5s, INP under 200ms and CLS under 0.1.
- LCP — optimize images and prioritize above-the-fold content.
- INP — split JavaScript and avoid blocking the main thread.
- CLS — reserve fixed dimensions for images, fonts and ads.
How we hit 95+
We start with architecture: server-side rendering, route-based bundle splitting and lazy-loading everything below the fold. Images ship as device-sized AVIF/WebP; fonts load with font-display: swap so text appears instantly.
Performance is not a one-time task. It is a discipline in every pull request.
— Huy Nguyễn
Finally, we add real-user monitoring (RUM) to track metrics on real devices, not just in the lab. That is the difference between a pretty number and a genuinely fast experience.
Eight years optimizing web performance for products at scale. Believes speed is a feature.