Front tracks are larger than the hind ones. The photo on the right shows a fox-eye view of a fox trail along the river bar. Note how the prints overlap. Each print is actually a hind print on top of a front one. The front track is on the right and the hind track is on the left in this photo.
Front track is larger.
The hind track appears skinnier. The claw marks are far ahead of the toes, indicating fairly long claws. The gray fox is the only canine that can climb trees. Perhaps these long claws help it climb. The hind track of a gray fox cast in plaster of Paris.