Document.visibilityState

The Document.visibilityState read-only property returns the visibility of the document, that is in which context this element is now visible. It is useful to know if the document is in the background or an invisible tab, or only loaded for pre-rendering.

Possible values are:

visible

The page content may be at least partially visible. In practice this means that the page is the foreground tab of a non-minimized window.

hidden

The page content is not visible to the user. In practice this means that the document is either a background tab or part of a minimized window, or the OS screen lock is active.

prerender

The page content is being prerendered and is not visible to the user (considered hidden for purposes of document.hidden). The document may start in this state, but will never transition to it from another value. Note: This was removed from the standard. Check compatibility table for details.

When the value of this property changes, the visibilitychange event is sent to the Document.

Typical use of this can be to prevent the download of some assets when the document is solely prerendered, or stop some activities when the document is in the background or minimized.

var string = document.visibilityState

document.addEventListener("visibilitychange", function() {
  console.log( document.visibilityState );
  // Modify behavior...
})