Why are french bulldogs SO small?

The reason French Bulldogs are so small is a result of selective breeding over many years. The practice of selective breeding focuses on mating animals with desired traits to produce offspring with those same traits. In the case of French Bulldogs, breeders wanted to accentuate their small size and other desired characteristics.

Furthermore, health factors attributed to the breed have contributed to their diminutive stature. French Bulldogs are prone to a condition known as achondroplasia which affects bone and cartilage growth. Due to this condition, the breed often experiences limb shortening and other skeletal changes that lend them their iconic body type.

Selective breeding and health aspects such as achondroplasia are the main reasons why French Bulldogs are so small compared to other dog breeds.