The Website Speed Checklist That Actually Moves Core Web Vitals

Almost every slow website fails on the same handful of things. Here's the checklist that actually moves Core Web Vitals — framework-agnostic, no fluff.

Measure first

PageSpeed Insights: mobile field data. LCP (load), INP (interactivity), CLS (shift). Fix in that order.

Images (biggest win)

• WebP/AVIF, sized to their slot (not 3000px into 400px)
• loading="lazy" below the fold
• Preload the hero (it's your LCP)

JavaScript (INP killer)

• Audit third-party scripts — chat/analytics/ads are often the heaviest thing
• defer/async non-critical scripts
• Code-split heavy features

Fonts, caching, CLS

• Self-host fonts, font-display: swap
• Long cache headers + a CDN + Brotli
• width/height on everything → no shift

The uncomfortable one

If you've done all this and you're still slow, the template is the problem. Page-builder themes ship MBs you can't optimize away.

Need a lean base? Browse fast DesignToCodes templates.

What's the worst offender you've found in a Lighthouse audit? 👇