TLDR
The Page Visibility API is especially useful for saving resources and improving performance by letting a page avoid performing unnecessary tasks when the document isn't visible. Pages only become hidden when the user switches tabs or minimizes the browser window containing the tab. API sends a visibilitychange event to let listeners know the state of the page has changed. API provides events you can watch for to know when a document becomes visible or hidden, as well as features to look at the current visibility state. API is available in modern browsers (Firefox 58+ Chrome 57+)via the TL;DR App
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Written by mozilla | Mozilla (stylized as moz://a) is a free software community founded in 1998 by members of Netscape.
