WebP isn't served on AMP websites
AMP doesn't support picture tags so that's the reason why ShortPixel Image Optimizer isn't able to serve WebP images on AMP websites if you have activated the option Using the <PICTURE> tag syntax
However, there is a workaround available published by @westonrouter.
- Go to https://gist.github.com/westonruter/332abdb2adefc6b204ad6fcc1beecedf
- Click on Download ZIP.
- Upload it to your WordPress dashboard, on Plugins > Add New > Upload Plugin.
- Clear your cache. Please do it in this order:
- Cache plugins (WP Rocket, LiteSpeed Cache, SG Optimizer...)
- Server cache (SiteGround, Bluehost...)
- CDN cache (Cloudflare, StackPath...). Please do it from your CDN's dashboard, not through your cache plugin or hosting dashboard.
- Browser cache (Chrome, Firefox, Edge, Safari...)
We're looking into other possible solutions to this issue and we'll implement them if we find any.