Is mooning a sin

Answer 1

It probably depends on your religion, but in general I would say that it could be a minor sin. I don't think it is mentioned specifically anywhere in a commandment, but God doesn't usually favor public nudity, and asks people to be modest in the way they dress and act.

In terms of repentance though, I think you could probably just pray and tell God that you are sorry. And stop doing it. ... Unless you have disrupted a public meeting or offended someone personally, there is probably no additional formal repentance necessary.