Could you tell me if my hairline is receding at 21 or if I have a mature hairline? (Photos)

If you r hair line was lower and is now much higher than before May be you are receding. Some receding as you get older is normal. That is the reason we do not jump into hair transplant procedures at young age. If your receding continues and also leads to hair loss in other parts of your scalp, in that case you may be having genetic male pattern hair loss. If you are concerned, it could be a good idea to see a hair transplant specialist.