A viper is a type of venomous snake belonging to the family Viperidae, which includes more than 200 species of snakes found in most parts of the world, except for Antarctica, Australia, Hawaii, Madagascar, New Zealand, and various other isolated islands. Vipers have long, hinged fangs that permit deep penetration and injection of their venom, and they are characterized by a pair of long, hollow, venom-injecting fangs attached to movable bones of the upper jaw that are folded back in the mouth when not in use. They are also known for their vertically elliptical, or slit-shaped, pupils that can open wide to cover most of the eye or close almost completely, which helps them to see in a wide range of light levels. Vipers are nocturnal and ambush their prey.

In addition to the snake, VIPER is also an acronym for a design pattern for software development that develops modular code based on clean design architecture. The modules in VIPER are protocol-oriented and each function, property input, and output is performed by way of specific sets of communication rules. VIPER is often used to develop smartphone apps and is heavily used in iOS along with Swift, Apple’s programming language.