A number of physical traits distinguish the canids. Intermediate in size among mammals, canids range from the tiny fennec, which weighs less than 2 kg (4 lb) to the imposingly large gray wolf, which can reach 80 kg (176 lb). Most canids have compact, fur-covered bodies and long, bushy tails. Many have a patch of dark fur on the top of the tail near its base, marking the position of a scent gland. Canids have a long, pointed snout and mouth. Their ears are usually erect, often pointed, and can be quite large in some species; bat-eared foxes, for example, were named for their conspicuously large, wide ears that better resemble those of a bat than a fox.

Canids have a large number of powerfully built teeth used for killing and holding prey, in fighting, and in threat displays. While most canids have 42 teeth, some species such as bush dogs have only 38 teeth while bat-eared foxes have 50. Like humans, canids have different types of teeth that are distinguished by shape, position in the mouth, and function. The chisel-like incisors, used for cutting food and in grooming, are located in the front of the mouth. The incisors are followed by a pair of dagger-shaped canine teeth used in fighting and hunting. Premolars and molars, located near the back of the mouth, are used for grasping, slicing, and crushing meat and bone. The molars at the very back of the mouth are adapted for feeding on items such as insects, fruit, and leafy vegetation, as well as meat. Some canids include a high proportion of fruits, seeds, and other vegetable matter in their diets.

All of the canids are excellent hunters, with keen senses of smelling and hearing, although their eyesight is not exceptional. They usually prey on mice and other rodents, rabbits, antelope, caribou, and deer—depending on their species and habitat. Canids are well adapted for long-distance pursuits of prey. They can run exceptionally fast and have remarkable endurance for covering long distances. For example, greyhounds have been clocked at 70 km/h (44 mph) and African hunting dogs can maintain speeds of 50 to 60 km/h (31 to 37 mph) for several kilometers.