I switched 23 sites from JPEG to WebP/AVIF last month — here's what I learned

I spent last month migrating 23 client sites from JPEG/PNG to WebP and AVIF. Here's what I wish someone told me before I started.

AVIF vs WebP: the real numbers

AVIF is about 30% smaller than WebP at the same quality level. But Safari support is still patchy — if your traffic is 40%+ iOS, you need <picture> tags with WebP fallback. No way around it.

The biggest win wasn't the format

The single biggest reduction came from capping max image width at 1200px and setting quality to 80. One site went from 9.4MB to 318KB per page — a 97% reduction — just from those two settings plus lazy loading.

The format switch was the cherry on top, not the cake.

Tools I used daily

works locally in-browser, no uploads.