If you have two macOS accounts on a single machine and want to merge them into one, macOS doesn’t offer a simple way to carry this out, but it’s nevertheless not very difficult. While you can mess around with file and folder permissions, my suggestion is to kill multiple birds with one stone by archiving and deleting the unwanted account.
Confirm there’s nothing in the old account you need to access from there to export.
Contacts, reminders, calendars, notes, and Safari bookmarks. These five kinds of data can be tricky to deal with if iCloud sync is off in the macOS account you’re getting rid of, and you have just the raw data available in your consolidated macOS account. Instead, follow the directions in this article about deleting your Apple ID, as the instructions are identical for ensuring you’ve exported data.
Mail. Again, it’s easier to export local mailboxes than to extract them from migrated data.
Data stored within apps. For non-Apple apps, make sure you don’t have data stored in such a way that you can’t access it by launching the app and opening a database, macOS package file, or similar item in your consolidated account.
Out with the old, merge with the new
Warning! Before proceeding, force a backup via Time Machine, make a local clone, or perform another backup operation to be sure you don’t lose any data unintentionally.
In the Users & Groups preference pane, click the lock icon in the lower-left corner and enter your administrative password.
Select the user that you don’t want to keep and will merge with another.
Click the minus (-) icon at the bottom of the list.
macOS prompts you how to proceed. Select “Save the home folder in a disk image.”
Click Delete User and confirm.
When that operation completes, the old account is removed from the system, in the Users directory is a disk image. You can double-click that disk image file to mount it, and then copy files or use the import function in any app that offers it to bring material over. One of many different apps that sync files from different locations could be useful, too, in copying over only files that don’t already exist in your consolidated account if you had any duplication between the two accounts’ files.
If you had two separate Photos libraries, one in the old account and one in the new, and you want to merge them, you likely need PowerPhotos from Fat Cat Software ($29.95), the only tool that offers a way to merge Photos libraries.
This Mac 911 article is in response to a question submitted by Macworld reader Ruth.
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