When I was on my first (and only) tinder date, we arranged the date, and I told her over text 2-3 days in advance. That way she could call it off (whatever the reason) if she was really scared of what this stutter thing might me. Which you have to respect, honestly. Not that she would tell you if that was the reason. I went with something like this: «Hey, I just wanted to let you know that I have a stutter. It’s a form of speech impairment. I usally don’t care much about it [even though I sometimes do lol], but I thought I should let you know». Then she asked me if I got nervous meeting new people because of that, and I replied yes a little but that I told her for her sake and that I didn’t really know when to tell her. She understood that, of course, and I’m really glad I told her. I was much more comfortable going to the date. Unless you have a really severe stutter, I recommend NOT talking too much about it on text or in person unless she asks you. If you do it can make her (and you) think too much about it. Also, your stutter is not your whole personality, so why make it a bigger deal than it is?