Instructions
Look at the tail of each cat. Japanese Bobtails have very short tails while Manx kittens are usually born with no tail at all. Manx cats may have short, stump-like tails similar to the Bobtail. A Manx may also be born with a long tail which is something never seen in a Japanese Bobtail.
Compare the height of the two cats. Japanese Bobtails are traditionally taller cats than the Manx.
Look at the physical build of each cat from the front and the side. Manx cats are stockier with shorter legs while Japanese Bobtails are typically leaner with a refined appearance.
How to Compare a Manx to a Japanese Bobtail
The Japanese Bobtail and Manx breeds of cats share some similarities. Their faces share similar shapes, and at first glance their bodies may appear the be the same. They are both also commonly without the long tails of most breeds of cats. Either can have short or long hair. Despite these similarities, the cats share no common ancestor. The Japanese Bobtail is originally from Japan by way of Korea while the Manx is believed to have originated on the Isle of Man near England.