I've not tried that, during development it was a texture max size issue? I figured it was just a weird Firefox bug. Didn't look too much into it due to most people using Chromium based browsers anyway
All of the Unity games that were using the default WebGL template with the integrated fullscreen button did not fullscreen at all, so it’ll be that and not something else. Make sure you use a template that autoscales to the available width and height when using Itch.io’s fullscreen button though.
