Should I tell my daughter her boyfriend is cheating on her?

Stay out of it, this is something she has to learn on her own. It'll backfire in your face if you do. I know it sucks.

I decided to look through my daughters boyfriends text messages

And stop going through other peoples stuff

What if he hacked you computer?

I agree with Mrs_Harsh Stay out of it. She is an adult. let her kearn from her own experiance. after she breaks up with him. Then tell her what you know.

hes a grown man and evidentally she is a woman, WTF is your problem??? Stay out of peoples SHIT!

I would try to warn her about him, but I wouldn't tell her how you came to suspect him. I once played detective and helped my son catch a girlfriend redhanded. She was lying to him, and I knew it, so I found out where she was going to be at a specific time and asked him to go for a ride with me. He saw for himself what she was up to, and I never had to accuse her of anything. How you came to know what you know doesn't have to be shared with anyone, but you can find out what you need to know and go from there. Be cool and be smart. I think we moms owe it to our children to keep them from major screw-ups if we can!

You found out in the WRONG way!!! So because of the way you found out, you can't tell her. It was very childish of you to look through his phone. AND truly, you don't know anything for sure. You just saw text messages. If he is a charmer, he will totally turn it around and you will be the bad guy.

TELL HER

ask yourself this... if you were her, would you want to know?

Depends. I would tell my daughter.

Do NOT tell her what you did! She'll never trust you again!
Talk to her about your concerns but don't ruin your relationship with your daughter!
Be there for her when and if they should break up, let her learn on her own, I know it's hard but you have to let her grow up!

While I understand the disdain of some above at your snooping... me, personally, I am VERY honest with my daughter from A to Z. She would be pissed that I was snooping (not something I would normally do but have done when in the past suspecting my own boyfriends - women's intuition is very powerful and accurate and sometimes it helps the decision making process to have evidence), but in the long run she would know that I did it to protect her. While it is true that she is an adult and needs to make her own mistakes like I did, she still respects my advice as her mother, whether or not she listens. The times she doesn't I continue to support her as her mother and am there without saying I told you so... (well, sometimes I say it but she already knows at that point).

Just admit that you were wrong to snoop but explain why at the time you lost your head but the info is still what it is. Encourage her to not move in...