The smallest snake ever found in the world is the Barbados threadsnake, called the Leptotyphlops carlae. The snakes are only about 4 inches long.
The Barbados threadsnake is a blind species of the threadsnake family. In width, it is about as large as piece of yarn. They are likely the smallest possible species; if they were much smaller, the babies would have trouble finding food. However, the babies are relatively large for their size when hatched, at half the size of an average adult; therefore, the snakes tend to only have one egg as a time due to space restraints in the mother's body.