As commented by developer.mozilla.org/docs
about Fullscreen API Browse compatibility, the requestFullscreen()
and other methods are deprecated (say also "Not for use in new websites").
But is not easy to obtain full-screen video in one-click, even with your hosted video and using iframe
... There are some HTML5+Javascript alternatives?
PS: help also github.com/whatwg/fullscreen.
You're misreading MDN.
document.fullscreen
is deprecated. someElement.requestFullScreen
is not.