The following iframe should not display the fullscreen icon. It’s not allowed because of security issues. Imagine a spammer taking control over blank.page and then…
I sometimes imagine a better world where security doesn’t matter, because you trust all parties involved. It’s like leaving your door unlocked because you live in a safe neighborhood. Another part of me is deeply skeptical about it, saying “leave your door unlocked on the internet, there’s bots blindly turning doorknobs and eventually one will come to open it.
The case for not allowing fullscreen functionality on iframes is—I think, sane, because the proper way of implementing it is through the parent window. Unfortunately, in implementation terms this means that in order to offer a fully featured blank.page embed, we’ll have to also provide a javascript snippet.
All right, let’s hit publish and see if the fullscreen icon appears: