Website Performance Optimization Guide: Achieve Lighthouse Score 90+

Why Speed Matters

In the digital age, speed is currency. A slow website doesn't just frustrate users; it costs you money. Studies show that a 1-second delay in page load time can yield a 7% reduction in conversions. Furthermore, Google uses page speed as a direct ranking factor for mobile searches.

If you want to rank higher on Google and convert more visitors, you need a fast website. In this guide, we'll walk you through the strategies we use at FUEiNT to consistently achieve Lighthouse scores of 90+.

Understanding Core Web Vitals

Google's Core Web Vitals are a set of metrics that measure real-world user experience for loading performance, interactivity, and visual stability.

Largest Contentful Paint (LCP): Measures loading performance. To provide a good user experience, LCP should occur within 2.5 seconds of when the page first starts loading.
First Input Delay (FID) / Interaction to Next Paint (INP): Measures interactivity. Pages should have a FID of 100 milliseconds or less.
Cumulative Layout Shift (CLS): Measures visual stability. Pages should maintain a CLS of 0.1. or less.

How to Measure Performance

The industry standard tool for measuring performance is Google Lighthouse. You can run it directly in Chrome DevTools or use PageSpeed Insights.

Lighthouse provides a score from 0 to 100 based on:

Performance
Accessibility
Best Practices
SEO

Optimization Strategies

1. Optimize Images

Images are often the largest assets on a webpage.

Use Next.js Image Component: If you're using Next.js, the <Image /> component automatically handles lazy loading and resizing.
Modern Formats: Serve images in WebP or AVIF formats, which are significantly smaller than JPEG or PNG.
Compress: Use tools like TinyPNG or ImageOptim before uploading.

2. Code Splitting & Lazy Loading

Don't send code the user doesn't need.

Route-Based Splitting: Next.js does this automatically. Each page only loads the JavaScript required for that page.
Lazy Load Components: Use React.lazy() or next/dynamic to load heavy components (like modals or charts) only when they are visible.

3. Minimize Main Thread Work

Heavy JavaScript execution blocks the main thread, delaying interactivity.

Reduce Third-Party Scripts: Audit your tracking scripts and chat widgets. Do you really need all of them?
Web Workers: Offload complex calculations to a background thread.

4. Implement Caching

CDN: Use a Content Delivery Network (like Vercel Edge Network or CloudFront) to serve static assets from a server closest to the user.
Browser Caching: Ensure your server sends the correct Cache-Control headers.

5. Font Optimization

Fonts can block rendering.

Display Swap: Use font-display: swap; in your CSS to show a fallback font while the custom font loads.
Self-Host: Hosting fonts locally (or using next/font) prevents layout shifts and connection delays to Google Fonts.

Conclusion

Achieving a 90+ Lighthouse score isn't a one-time task; it's an ongoing process. As you add new features and content, you must continuously monitor your performance metrics.

At FUEiNT, performance is baked into our development process. We build lightning-fast web applications that delight users and satisfy search engines. If your website is sluggish, get a free performance audit from our team today.