Notifications aren’t done by the browser holding open a socket to individual sites; there’s a somewhat complicated protocol involving a service run by the brows

Notifications aren’t done by the browser holding open a socket to individual sites; there’s a somewhat complicated protocol involving a service run by the browser manufacturer. I’m not aware of any web APIs that explicitly require the browser to hold idle connections alive in a socket pool (server-sent events/websockets are a different matter; but they involve an active worker of some description—and last I knew weren’t available in service workers); this is purely a performance optimization.