what does 'What are you up to?' mean?. Does it mean how are you or 'what are you going to do now?'
the second guess is correct.
'What are you up to? =) 'what are you going to do now?'
"What are you up to?" = What are you doing?
Usually used with friends either because you are interesting in what they might be doing, or because you might next want to invite them to do something together. (American English explanation)
In British English:
1. What are you up to?
If you suspected that a child was misbehaving, you might say "what are you up to?", in a suspicious tone. The child will invariably reply, in an aggrieved tone: "Nothing, why?"
2. (So,) what are you up to (these days)?
You might say this to a friend. It means "please give me a (brief) summary of your recent activities".