@spycrab Thought "huh, I'd like to be a girl" one day while watching a music video on tv. Then a few weeks later I saw an interview (also on tv) with a trans woman, and thought 'wow, so I can be a girl if I'm trans". Then I started researching how to be trans. And the stories (though being kinda sad, those being from the early '90s and all) resonated a little with me (mostly the yearning aspect; I later found better, more recent stories online that still resonated), so then I started doing the transition things, and that worked, so I guess that (both the doing that and the feeling better for it) confirmed that I was trans. It's been ~25 years and still no regrets, so yes, long-term confirmation too.
Feeling that I actually *am* a girl/woman is something that only gradually grew. It wasn't there at first, only a strong wanting to be a girl.