With the coyote, only the two foremost may show, but this is not very definitive. The size of the prints and length of the gaits is the most helpful feature. In other words, a small coyote may be no larger than a large fox. The numbers for the fox are in red, and those of the coyote in brown. Wild canines usually place their feet in a much straighter line than domestic dogs.
Coyotes tend to travel in bolder straight lines than foxes, and in more open spaces.
The fox may follow brush lines and meander more. If the snow is over a foot deep and soft, the heavier weight of the coyote may mean that body prints will also show. If the prints are extremely clear here are some other useful features to help distinguish them. Red fox have a bar of callous across the back of the rear pad which will show as a hard line. Coyotes have a concave back edge to the larger front paw print and a convex back edge to the smaller hind print.