How do I know if my boyfriend is on facebook with his phone?

[Elissa G]

Yesterday I saw that my boyfriend was on facebook at 3 in the morning. Usually when someone leaves it says "active 2 hours ago" or something. And this time it said "on mobile". So I'm really confused. does it mean he's on facebook or on his phone? before I start asking him what he was doing at 3 am, i want to understand how this thing works. How do you know if someone is really on their phone or not? because usually it always says when someone was active.

[Mary]

In all honesty, if it says "mobile" next to their name in the chat window, even at 3AM, that doesn't necessarily mean that he was awake and using his phone to get on facebook at 3AM.

When I use facebook on my computer, it won't say "mobile" next to my name in my friends' chat windows. But if I log out of facebook on my computer, and am logged into facebook on my phone, it will say I'm available via mobile, no matter the time of day/night, so long as I don't log out of the app on my phone, even if I'm not using it.