Is this a matured hairline or early male pattern baldness? (25, male, caucasian) (photos)

Maybe it is early genetic balding or maybe it is maturing hair line. You really cannot confirm a diagnosis with photos.

Yes, this looks like you might be having early pattern baldness.  Find a specialist in hair restoration right away and develop a long term plan for treatment.  There are a ton of great options including cellular therapy which have been show to be safe and effective for slowing the progression of hair loss. 

you may or may not be having genetic male pattern hair loss. Your hair line has receded a little but that could be normal progression of hair line. You need to see a hair restoration specialist to confirm the cause of your hair loss and if indeed it is generic male pattern hair loss then get started on a medical regiment routine. 

Yes, it looks like you have an early recession of your hairline. What will happen in the next
5 or so years is probably that you will continue losing hair in the pattern
that you inherited from your parents and grandparents. Your looks show early
balding now, but this is the time to meet with a good doctor who can make the
correct diagnosis and start you on the drug finasteride, which is highly
effective at stopping progressive balding and possibly reversing it in men of
your age. Get Bulk Measurements of your hair to determine where your present
balding is now, and then after you go on the medications, such measurements
will tell if the treatment is working within a year or so. If you are
developing a more advanced balding pattern which the Bulk Measurements will
show over a one year time frame, then you and your doctor need to develop a
MASTER PLAN and that Master Plan might have transplants as an option. With
early balding, I would not rush to hair transplants if the drug alone will
solve the problem and you will know this within a year.

The photos show some frontotemporal recession and some miniturized hairs. Therefore I would say that you do have male pattern alopecia.  You can do a genetic test on 23 and me to confirm.  The issue is how far will it extend, and that I can't tell you.  It might stay at this state or progress.  Only your family history can dictate this.