Document.fullscreenEnabled

The read-only fullscreenEnabled property on the Document interface indicates whether or not full-screen mode is available. Full-screen mode is available only for a page that has no windowed plug-ins in any of its documents, and if all <iframe> elements which contain the document have their allowfullscreen attribute set.

Although this property is read-only, it will not throw if it is modified (even in strict mode); the setter is a no-operation and it will be ignored.

var isFullscreenAvailable = document.fullscreenEnabled;

A Boolean value which is true if the document and the elements within can be placed into full-screen mode by calling Element.requestFullscreen(). If full-screen mode isn't available, this value is false.

In this example, before attempting to request full-screen mode for a <video> element, the value of fullscreenEnabled is checked, in order to avoid making the attempt when not available.

function requestFullScreen() {
  if (document.fullscreenEnabled) {
    videoElement.requestFullScreen();
  } else {
    console.log('Your browser cannot use fullscreen right now');
  }
}

• Fullscreen API
• Guide to the Fullscreen API
• Element.requestFullscreen()
• Document.exitFullscreen()
• Document.fullscreenElement
• :fullscreen and ::backdrop
• The <iframe> allowfullscreen attribute