You can cheat on anyone without even having sex. Cheating is an intent, it is a feeling of going on ahead with someone else. While physical affair might not hurt as much as emotional devastation does. 
Personally, I would be forgiving of a physical affair because that is just sex and sex is nothing but an orgasm. While getting tangled emotionally with someone is altogether depressing.
And distancing yourself later is even more. While all these little things might let you cheat without having sex, it will eventually add up to the demise of your relationship.

1. Sexting with anyone

If you are trying to get off someone else, you are pretty much kind of cheating on the one you are currently with. We know it's just texting but in any ways it's sex. via

2. Creating profiles on dating apps. 

Don't give away the crap that you are just trying to see what's out there? Because if you would have been that curious, you wouldn't have been in a relationship in the first place.

3. And, using them.

This is even worse. You installed the app because you were inquisitive. Not fair. If you use an app with intent to date new people, you are cheating.via

4. Creating multiple alternative personas online. 

It is catfishing and catfishing is never cool. via

5. Taking flirtation too far with a friend.

Yes, it happens. It has happened to me a lot of times and that is not a big deal. People flirt a lot. But taking it too far with a friend might be wrong. You don't want to end up having a sudden breakdown, do you?via

6. Comparing your guy/girl with every other person you like.

It is never fair to compare your partner to anyone. Comparing him/her you have mere feelings for, however, that's just wrong. via

7. Carrying a virtual relationship.

So, you stalked them a little on the various social network but then you may never do anything physical or emotional, and it is just texting but it may cross lines anyways. via

8. Withholding sex because you are thinking about someone else.

In any ways, that will be counted as cheating. You are holding on to your crush and not being intimate with the person who has been there for you the entire time is cheating. via

9. Sending photos

Sending risque pictures with anyone but your partner is just a big No..No. via

10. Sending videos.

This goes pretty same the way it goes for the pictures. via