The History interface allows to manipulate the browser session history, that is the pages visited in the tab or frame that the current page is loaded in.
The History.length read-only property returns an Integer representing the number of elements in the session history, including the currently loaded page. For example, for a page loaded in a new tab this property returns 1.
The Window.history read-only property returns a reference to the History object, which provides an interface for manipulating the browser session history (pages visited in the tab or frame that the current page is loaded in).