Bulldogbreeds.com lists 14 different types of bulldogs. Some of these breeds include the American bulldog, French bulldog and English bulldog. Bulldogs are characterized by their large heads, muscular builds, shortened muzzles and pushed-in noses.

The bulldog gene pool has been modified over the centuries through selective breeding and out-crosses to create new breeds. Bulldogs have been bred to adapt to local living and working conditions, thus resulting in differences in size and appearance. The French bulldog, for example, was bred as a companion dog suitable for small spaces. The American bulldog is an athletic dog of medium build bred originally for farmwork.