Hello.
I have never heard this phrase "what are you up to". Is it common?
Thanks.
Very common.
You walk up to your friend, who is sitting with electrical parts all around him.
You: Hey, Boris, what are you up to?
(I'm trying to repair my alarm clock.)
You come upon your daughter, who has made a complete mess in the kitchen but appears quite happy.
You, trying not to sound alarmed: Hi honey. Um... what are you up to?
(I have to bring cupcakes to school tomorrow and I'm doing it all by myself!)
You see a friend you haven't seen in a couple months
Hey, ems! What have you been up to lately?