Microchip

A microchip is a small glass-covered transponder, about the size of a grain of rice, that a vet or trained person injects under the skin, usually between the shoulder blades. It has no battery and no tracking function. When a scanner passes over it, the chip sends out a unique number. Shelters and vets scan found cats and use the number to look up the owner in a registry.

The chip is only useful if the registry record is correct. Register the number as soon as it is implanted, and update your phone number and address after every move. Many cats that carry a chip cannot be reunited with their family because the record was never made or never updated. A collar and tag are still worthwhile, since anyone can read a tag without a scanner, though collars can slip off or be lost.

Implanting takes seconds, needs no anesthetic, and many vets do it during a spay or neuter. In rare cases a chip moves, so scanning the whole body is standard practice. Ask your vet to scan the chip at each annual visit to confirm it still reads. Some places require microchipping by law, and the rules differ from one country to the next.