A microchip is positioned as permanent identification. After implantation the registration must be completed, and a finder or shelter needs a scanner to read the contact details.

A collar tag is visible, so a passer-by can call without equipment, but a collar can slip off or catch on something.

Indoor cats can still get out. A chip plus a lightweight tag is the steadier combination, and the collar should have a safety release.

Implantation and registration updates should go through proper channels, and details must be updated after a move or phone change.