How to fix a slow website: a Core Web Vitals checklist

Short answer: most slow sites are slow because of oversized images, render-blocking scripts, too many third-party tags and no CDN. Fix those four and you will pass Core Web Vitals on most pages.

The three numbers that matter

• LCP (Largest Contentful Paint): under 2.5 seconds. How fast the main content appears.
• INP (Interaction to Next Paint): under 200 ms. How quickly the page responds to taps and clicks.
• CLS (Cumulative Layout Shift): under 0.1. How much the layout jumps while loading.

Fix LCP

1. Serve images in AVIF or WebP with responsive sizes.
2. Preload the hero image and never lazy-load it.
3. Put the site behind a CDN with full-page caching where possible.
4. Self-host fonts and use font-display: swap.

Fix INP

1. Audit third-party scripts — chat widgets, heatmaps and tag managers are frequent culprits.
2. Break up long JavaScript tasks and defer non-critical work.
3. Ship less JavaScript: server-render pages and hydrate only interactive parts.

Fix CLS

1. Always set width and height on images and embeds.
2. Reserve space for ads, banners and cookie notices.
3. Avoid inserting content above existing content after load.

Why it matters for revenue

Faster pages rank better and convert better. On e-commerce sites we routinely see conversion rates rise 10–30% after a speed overhaul — before any design changes.

Want to know where your site stands? Request a free SEO audit and we will send you a prioritised fix list.