Why are footprints considered to be a fossil?

footprints are found in rocks only.
footprints can be dug from the ground.
footprints are imprints of a living organism.
footprints can be preserved for a long time.

Footprints are considered to be fossils because they can be preserved for a long time.

Explanation:

The reason footprints are considered as fossils is that there are certain attributes of fossils that the footprints also have. Footprints help determine the size, and apparently the age of the animal. They also themselves clarify which animal is the footprint of. Moreover, like the evidence of any other physical fossil, footprints also dispense information about the period depending on where and what state it is found in.