おつかれ as a greeting for friends?

I use お疲れ様です/お疲れ様でした at work when I'm leaving or someone else leaves, but I also hear people use it as a greeting when they see their friends a lot. Whenever I look up definitions though, it's never talked about as an informal greeting, so I've been reluctant to use it in case I'm missing some of the nuances.

When do I use お疲れ when I'm talking to friends outside of work? (I'm in 関西 if that makes a difference).

ありがとうございます！