There are a million resources out there explaining that iOS browsers don't support the fullscreen web API.
But I know there is a way to do landscape fullscreen on iOS. See these examples:
When you go to those pages, they tell you to rotate your phone to landscape, and once you do - the entire phone UI is gone. True fullscreen.
I just can't figure out what's the API for doing that.
I just figured it out. Boy do I feel silly.
There is no API.
Just browse to any page on Safari iOS, rotate your phone to landscape, and bam, you're in fullscreen mode.