What precisely changes the "last seen" time?

[tentativeuser]

Background: my phone was stolen, and after it was stolen, someone else pointed out to me that my "last seen" time on Whatsapp was more recent than when I'd last had my phone. I assumed that the number changed because my phone had been opened, even though my phone has fingerprint lock activated and that seemed unlikely.

Someone else said to me, on the other hand, that the number updates every time one's phone is turned on. It also occurs to me that because Whatsapp notifications appear on my lock screen and it is possible to send replies from the lock screen without ever unlocking the phone, someone might have been able to be "seen" by Whatsapp without getting past the lock screen.

What's the truth? Under what circumstances will the "last seen" time on an Android phone with Whatsapp update?

 

[SpookDroid]

Nope, Whatsapp updates the 'Last Seen' on the last active session you have. This can be through the phone app, the web app, or the desktop client. As for the lockscreen notifications, if those don't need your phone to be unlocked, then yes, acting on the notification would count as an 'active' session.