The CTZ file extension is associated with a program called Custody Toolbox. It is an organizer software dedicated to guardians of children who find themselves in a difficult situation, e.g. after divorce, and raise children together with their ex-spouse. It includes, among others, a journal, calendar and address book.

CTZ is a file used to back up Custody Toolbox data. In case of unexpected problems with the program, such a compressed archive allows to recover the existing data (e.g. after reinstallation or after the program database has been damaged). This solution is also used when transferring the program to another device.