Is it flirting if a guy randomly touches your back while talking?

I have a guy friend that I've known for a little while now, but not super well. We met through mutual friends and go to several group events together. We've always had a good time chatting, but lately it seems a little different. We were at an event a couple weeks ago and we got talking. We were teasing each other and joking around. Out of the blue while we were laughing he put his arm around me and put his hand on my back. It surprised me because he's never done anything like that before, we've just chatted here and there. And we were bs'ing so it wasn't like a serious convo where he was comforting me. He'd also look at me when he cracked a joke to the group, and if I was laughing he'd laugh harder. At one point he joked that he was really good looking. I'm just curious, was he just being friendly or was he flirting? I'm awful at reading these things.

Is it flirting if a guy randomly touches your back while talking?
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