It depends on the partner’s feelings about it. Some women are very adamant their partners never look at porn. I’ve noticed that often on here.
Personally, I haven’t given it too much thought. I was not aware if any of my bf’s did. One of my bf’s frequented strip clubs, and I never objected to it. But that relationship never became committed and ended.
My husband never gave me reason to think about if he was looking or not. There was a time, though, where he spent a lot of time on this porn joke website that was free. It didn’t bother me until we were really having problems where I felt he was not showing interest me in, and I felt resentful he had interest in that site. The site went out of business, so that was the end of that.
He’s not a frequenter of strip clubs. He’s gone on rare occasions, and I have no problem with that. I’ve even gone with him a few times. I’d only have a problem, if he frequented them.
I give him his privacy and wouldn’t demand to see his phone to see if he looks at porn. So if he does, I don’t know, and I don’t care.
As for all things that are cheating, you could say that even having fantasies about others is cheating. Aren’t we all guilty of that in some form?