These guides are designed for identification “in the field” where you might be looking at live crabs by eye or through binoculars or from photographs. I will generally try to avoid characters that will require you to physically catch the crab, although I do mention a few for secondary verification. They do not include the more strict taxonomist-style characters that may only be visible under a microscope or via dissection. It is also assumed that the individuals are living, as death (and even capture) can cause dramatic color change.
You can choose a guide from the list below or click on the following map to go to the guide for that region. The various location information pages also include links to relevant guides for each location.
The western Atlantic and eastern Pacific Realms are roughly organized from north to south, while the Indo-West Pacific Realm is roughly organized west to east (or perhaps clockwise) starting from South Africa.