Currently WebKit is the only rendering engine using the prefixed property for fullScreen: window.document.webkitFullscreenElement the standard property is implemented on Gecko and Blink. See https://developer.mozilla.org/en-US/docs/Web/API/Document/fullscreenElement#browser_compatibility It is probably time to add aliases * fullscreenElement <- webkitFullscreenElement. * requestFullscreen <- webkitRequestFullscreen * exitFullscreen <- webkitExitFullscreen it is common to see code such as ``` { key: "isFullscreen", value: function() { return window.document.fullscreenElement || window.document.webkitFullscreenElement || window.document.mozFullScreenElement || window.document.msFullscreenElement } } ``` This can't be fully removed because of probable webcompat breakage. worse it encourages code like this. (if you read this, do not do that) ``` const isFullScreenCapable = document.fullscreenElement || document.webkitFullScreenElement; const isWebkit = document.webkitFullScreenElement; if (isFullScreenCapable) { if (isWebkit) { document.webkitExitFullscreen(); } else { document.exitFullscreen(); } } if (isWebkit) { canvas.webkitRequestFullscreen(); } else { canvas.requestFullscreen(); } ``` and allow for fingerprinting.