Cannot upload webp

I am creating a new theme and I would like to have my photos be in webp Format. When I try to upload them using the admin panel it tells me that I need to convert them to jpg or gif. It is a new install so it is up to date. I have tried editing botg htaccess and functions.php although since WordPress should support by default I shouldn't have to do that I don't think anyways.

Any suggestions?

Thanks