A slow site drives visitors away and hurts your SEO. Here is a concrete guide to achieving Lighthouse scores above 90 without redoing everything from scratch.
Why speed is critical
According to Google, 53% of mobile visitors abandon a page that takes more than 3 seconds to load. On an e-commerce site, each additional second of latency can cost up to 7% of the conversion rate.
The main levers
1. Optimise images
Images often represent 60 to 80% of a page's weight. Use WebP or AVIF formats, resize to actual display size, and use the loading="lazy" attribute to defer loading.
2. Limit third-party scripts
Each tracker, social widget, external chat adds requests and blocking JavaScript. Audit what is truly essential.
3. Cache aggressively
A good CDN with a well-configured cache policy transforms the experience for returning visitors.
4. Favour SSR or static generation
Serving ready-made HTML instead of waiting for JavaScript to build the page changes everything, especially on mobile. Frameworks like Angular SSR, Next.js or Astro make this accessible.
Measure to progress
Without measurement, no improvement. Three free tools are enough:
- PageSpeed Insights for a quick audit.
- WebPageTest for detailed analysis by location.
- Search Console to track Core Web Vitals over time.
The goal is not perfection but continuous improvement. Aim for a score > 90 on mobile and > 95 on desktop.
