Image Optimization: The Fastest Win for Web Speed

On most websites, images account for the majority of page weight, which means they are usually the single biggest lever on load time and on your Largest Contentful Paint score.

The good news: image optimization is mostly mechanical. Here is the checklist we apply to every build.

Serve modern formats

AVIF and WebP deliver the same visual quality at a fraction of the file size of JPEG or PNG. Serve them with a fallback, and you cut weight dramatically with no perceptible quality loss.

Size for the slot, not the source

A 4000px photo rendered in a 600px container wastes bandwidth on every visitor. Generate responsive sizes and let the browser pick the right one, so phones never download desktop-sized assets.

Lazy-load below the fold, prioritize above it

Defer offscreen images so they load only as the user scrolls, and explicitly prioritize the hero image so it paints fast. Always set width and height to reserve space and avoid layout shift.

The takeaway

Modern formats, right-sized assets, lazy loading, and reserved dimensions are the whole game. It is unglamorous work, but no other change improves perceived speed for as little effort.