My car is giving me a message that my brake pads are low but it's not saying whether it is front or rear. The rear ones were replaced 25k miles ago, and the front ones were replaced 16k miles ago. Before I buy new pads, are they the front or rear ones?

 

youll have to look. rear usually wear much faster on these cars so my educated guess would be rear

 

It's hard to tell by looking through the wheel. Can you tell by looking at the pictures I posted below of the rear pad?

 

Yep, no way to tell without at least whipping the wheels off and having a gander down the sides of the pads.
Not a huge job to also remove the pads and properly inspect them.
The wear indicators are on the front left inner pad and rear right inner pad, the inner pads tend to wear more than the outer pads so whichever wear sensor has triggered should be the most worn pad. But you never know, some other pad may also be quite worn and/or ready to fall apart, best to have a good look at them all.
That said the wear indicators are meant to trigger when there is still plenty of pad material left (very wide safety margin) but they have been known to go the other way and not trigger until there is bugger all left and in some cases not trigger at all. I don't trust the system as far as I can throw it so I have disabled it on all of my Jags and instead I inspect the pads manually every couple of months.
DIY pad replacement is easy, only two "special" tools needed - a 9 mm hex driver for the front caliper pins (they are rare!) but you can get one from Amazon or Fleabay for not many $, and a brake piston wind-back tool for the rear pistons, again plenty of kits on Fleabay for not many $. You also need a 7 mm hex driver for the rear caliper pins but they are common.
While you are at it dump the stock horribly dusty (and often noisy) brake pads for some ceramic pads. Waaaaaay less dust, whisper quiet and nice progressive feel as opposed to the stock "on/off switch" feel in stop/go traffic. They also perform well enough for a daily driver and wear a lot slower than the stock pads, and they don't chew through the rotors as fast as the stock pads.
I fitted Power Stop Z16 ceramics all around on my old XFS a few years back and they were the best mod I ever made, I just wish they made them for my F-Type but they don't!

 

Autozone carries them also

 

no because I use a small pen led light to shine at the pad where it contacts the rotor to she the thickness. And I cant see that with yours. Sometimes I just have to take off the lf or rr wheels to have a better look because sometimes its like looking at your last pic
rotors don't look lipped, but just run your finger over the edge. Should still be flat if ok. I replace them when a lip has formed

 

Like this

 

I would check to see if the sensor wire has been incorrectly installed and has rubbed through , a bit of a cleche but ask me how i know.

 

I just had this message pop up on my car and changed all 4 of them. I bought Brembo pads on the front and TVS on the back + 4 sensors (you should change these if you got the message. Mine were torn in half).
Cost: 350 euros for parts and labor.

 

Don't buy 4 unless you want to have 2 in inventory. The XF only uses 2 sensors. Front left and rear right.

 

This is news to me. I'll make sure I didn't pay for 4 sensors. Thanks!