There’s a simple solution, although the method and nomenclature changes a bit with the different versions of OS X and macOS. The Contacts app lets you export its contents to a single file that you can easily move to another Mac or use as a backup. Here’s how.
Restore Contacts in macOS Catalina (10.15) Through Mountain Lion (10.8)
To put the contacts from your archive into your Contacts app:
How to Back Up and Restore Address Book Data in OS X Lion Through OS X Leopard
In older versions of OS X, Contacts was called Address Book. Here’s how to back up and restore its data file:
Restore Address Book in OS X Lion (10.7) Through OS X Leopard (10.5)
Restoring is similar to newer versions, too:
How to Back Up and Restore Address Book Data With OS X Tiger and Earlier
Here’s what the process looks like in even earlier versions of OS X:
Restore Address Book in OS X Tiger (10.4) and Earlier
Moving Address Book or Contacts to a New Mac
When moving your Address Book or Contacts data to a new Mac, use the Export option to create the archive, rather than create an Address Book backup. The Export function creates an archive file that’s readable by all the versions of OS X and macOS.
