As someone who stutters and used dating apps in the past, I say to disclose it before you meet. They most likely won't care if you stutter or not. They may be taken aback though if their first time knowing about it is when you meet up in person. I found disclosing first takes the 'shock factor' out of meeting someone for the first time and possibly stuttering. The last girl I talked to on a dating app I mentioned I stuttered. She didn't care. We're married now. She still doesn't care. ​ Ultimately it's your preference. Like mctommy said, it's when you feel comfortable doing so.