So I'm a little bit privileged in this area, I guess. I'm such a covert stutterer most of the time that I can pass for fluent on a date and bring it up at my leisure. Which is usually around the 2nd or 3rd date. However, I have to use online dating because of the social anxiety from stuttering as a child. Anyway, I'd say it depends on the severity. If you're like me and can get away without bringing it up until you want to, do that. If it's more overt I would bring it up on your online dating profile. Just once and don't make it a big out of it. You'll filter out some people but you don't want to be around those people anyway.