A practical checklist for 95+ Lighthouse

Why Lighthouse scores matter (and when they don't)

Lighthouse scores aren't a vanity metric — they directly correlate with user retention, conversion rates, and SEO rankings. But the goal isn't to chase 100s blindly; it's to ship a site that feels fast to real users.

The checklist

1. Images are always the bottleneck

Most "slow" sites I audit have image problems. The fixes:

• Use next/image with explicit width/height (prevents CLS)
• Serve AVIF/WebP with JPEG fallback
• Lazy-load below-the-fold images
• Use responsive sizes attribute

2. Font loading strategy

next/font does most of the work, but:

• Preload critical font weights only
• Use font-display: swap or optional
• Subset to Latin characters unless you need i18n

3. Layout stability

CLS under 0.1 requires discipline:

• Reserve space for images, ads, and async content
• Avoid injecting content above existing content
• Use CSS aspect-ratio for media embeds

4. JavaScript budget

Every kilobyte you ship is a kilobyte users pay to download and parse:

• Use Server Components by default in Next.js 14
• Code-split at route boundaries
• Audit third-party scripts quarterly

Measurement

Don't trust Lighthouse alone. Set up Real User Monitoring (RUM) with Vercel Analytics or similar — p75 LCP matters more than a lab score.