To answer this question, you need to start with what cheating is for you personally.
If you understand it as sex with another person, then it is unlikely that watching an 18+ video is equivalent to it.
If cheating is a broad concept for you, including an outburst of sexual energy outside of a relationship, and even without discussing it with you, then yes, porn can be considered cheating. But the question is actually much more serious than it seems!
Why do people hide their interest in porn movies? Often not at all because they consider it a cause for scandal. It’s just that modern society condemns such things, and they don’t want to justify themselves once again.
This aspect is also interesting: is self-satisfaction for the film – is it treason? Many believe that once a person is discharged in this way, it is bad for sex. In fact, this is usually not the case, and masturbation does not interfere with the couple’s intimate life in any way.
Now consider if watching porn is not an escape from a reality in which you constantly swear and stop having sex, as a result you can learn a lot about your relationship. And instead of scolding a loved one for watching adult films, you should sit down and calmly discuss the situation with him. It is quite possible that porn is just the tip of the iceberg, but in fact, you have long lost touch with each other and communicate only when necessary. Or do your best to pretend that everything is fine, because you don’t want to lose each other. Both situations are rather sad, but you can probably figure out how to change them to mutual joy.
And then the question of porn films, most likely, will cease to exist altogether.