How do google analytics detect the user leaves page?

Question

This is the context of a single-page application, but I believe it would happen as well in other cases. While the GA tracker get's updated with page changes I can see in the realtime report that the user is still alive. But when the user doesn't interact with the page for a while (while playing a video for example) it disconnects from the GA view.

I would like to better understand how GA works in this case, maybe I need send events to keep the user alive.

Answer 1

Google Analytics does not detect when somebody leaves the page. There is no reliable way to do that (unload handlers do not fire when somebody just closes the window). Instead Google waits till the session has ended - after 30 minutes without interaction (can be adjusted in Universal Analytics in the property settings) the session is ended and the vsitor has left as far as the reports are concerned (he might have left a lot earlier, but the time after the last interaction is not tracked in GA).

Plus a session can have 500 interactions at maximum, so there is no way to keep it alive indefinitely.