The Contacts programme on the Mac is a lifesaver
for keeping track of both personal and professional contacts.
To backup your Contacts database, follow these steps.
The Contacts app for macOS can be found in the Startup Disk's /Applications folder.
Each page or vCard that you add to a Contact is saved in a local database on disc at /Library/Application.
The AddressBook folder contains a number of files and folders, but the primary Contacts database is called "AddressBook.
Because the.abcddb file type is opaque, Apple doesn't make its specs available.