[NavinF]

You've almost certainly downloaded WebP images, but you didn't realize it because many websites serve multiple formats at the same URL. This is often done with a HTTP reverse proxy that automatically converts between formats so if you have a modern (last decade) browser, you'll get a WebP even if the download's file extension seems to be ".png". All modern image editors support WebP so you'll never notice the difference

[joveian]

On The Guardian for example it looks like I'm getting WebP for the photo collections and AVIF for the story images, both from .jpg URLs (in Firefox hit Ctl-I to see image info). Their photo galleries have been WebP for years. Firefox is clever enough to correct the suffix if you try to save it.

[noir_lord]

Cloudflare Polish and similar will transparently do it as well, as long as the Accept header contains webp.

[whywhywhywhy]

>All modern image editors support WebP so you'll never notice the difference

This support has always been overstated. Photoshop still doesn’t support it, you encounter other weirdness like Apple Preview.app can view them but not edit them.

[NavinF]

Photoshop definitely supports it: https://helpx.adobe.com/photoshop/kb/support-webp-image-form...

Preview.app is the exception to the rule, but it still has acceptable UX. After you finish drawing the first brush stroke on a WebP file, it will ask you to reopen the edited file as a tiff before you continue editing. No loss of data or functionality