Check with your city for any licensing or identification requirements for your pet. Usually purchased from the city, your pet is assigned a number which is tracked in a computer database. Tags are attached to your pet's collar. If your pet is found, the animal control officer can check the tag number, pull up your address, and call you to let you know they have your pet.
Tattoos are a visible and somewhat permanent method of identification.
Unlike tags, tattoos are not reliant on your pet wearing its collar. However tattoos usually fade over time, making them illegible. It is administered quickly and painlessly by a simple injection. If your pet gets lost, animal shelters or city pounds equipped with scanners will be able to scan your pet's body to quickly locate the ID number of the microchip along with the corresponding owner information. Many shelters and pounds these days are equipped to handle microchips.