Images use legacy formats
What this means
This page leans on JPEG/PNG/GIF files. WebP and AVIF typically cut the same image by 25-50% at equivalent visual quality, and both have had universal browser support for years. On an image-heavy page that is usually the largest single byte saving available.
How to fix it
Serve WebP or AVIF with a <picture> element that keeps the legacy file as a fallback source, or put the images behind an image CDN that negotiates format automatically.
Fix effort
This check needs review: the change can be drafted for you, but a person has to approve the wording or choose the target before it ships.
Authoritative source
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