I (22F) guess it depends on how visible your stutter is and how comfortable you are with it. I prefer not mentioning it on my profile. I feel mere strangers do not have to know that. It feels too personal. However, I will always mention it before a first date if I feel that I might stutter. My stuttering is very variable and depends on phases : sometimes I stutter a lot for a few weeks, than it goes away. In the latter case, I won't mention it before the first date since I feel the mere fact of mentioning it tend to reinforce it. And also, all of that raises the question : do I want to date someone who mind that I stutter ?