files/en-us/web/api/document/fullscreen/index.md
{{APIRef("Fullscreen API")}}{{Deprecated_Header}}
The obsolete {{domxref("Document")}} interface's fullscreen read-only property reports whether or not the document is currently displaying content in fullscreen mode.
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.
[!NOTE] Since this property is deprecated, you can determine if fullscreen mode is active on the document by checking to see if {{DOMxRef("Document.fullscreenElement")}} is not
null.
A Boolean value which is true if the document is currently displaying an element in fullscreen mode; otherwise, the value is false.
This simple function reports whether or not fullscreen mode is currently active, using the obsolete fullscreen property.
function isDocumentInFullScreenMode() {
return document.fullscreen;
}
This next example, on the other hand, uses the current fullscreenElement property to determine the same thing:
function isDocumentInFullScreenMode() {
return document.fullscreenElement !== null;
}
If fullscreenElement isn't null, this returns true, indicating that fullscreen mode is in effect.
{{Specifications}}
{{Compat}}