If your Mac warns that your encrypted backup drive won’t be compatible with macOS 28, you have time to plan. That version is expected in fall 2027, roughly a year from now. The warning concerns the older format used to store your backup. It does not mean the physical drive is broken or needs to be thrown away.
Which backup drives are affected?
Apple is ending support for encrypted Mac OS Extended volumes, also called HFS+, in macOS 28. If you have a drive that is affected, your computer may warn you when you back up. Apple’s modern APFS format is unaffected.
Why avoiding macOS 28 doesn’t solve the whole problem
You might reasonably think, “Then I won’t upgrade to macOS 28.”
That would let you keep using the backup with your current, compatible version of macOS. But consider one of the main reasons you have a backup: your computer could fail.
Suppose that happens after macOS 28 comes out. You buy a replacement Mac, and it arrives with macOS 28 installed. Now you need that backup, but it’s incompatible with your new computer.
Plan for the computer you might need to restore onto, not only the one you’re using today.
Two options to consider over the next year
This is an early warning, not a reason to disconnect your backup or rush into erasing it. Keep backing up while you plan the change.
1. Replace an older backup drive with an SSD
If your backup is on an older mechanical hard drive, this could be a good time to replace it with a solid-state drive, or SSD. You can read more about why I recommend considering an SSD for Time Machine, along with my current backup drive recommendations.
An additional advantage is that you can leave your existing backup untouched while you set up the new one.
A new backup starts a new history. But files on your computer when you set up the new backup will be on the new backup. What’s potentially missing are files you deleted or changed in the past. Keep that old drive if you still need its history, remembering that its older format will continue to require a compatible Mac.
2. Erase and reuse your existing drive
If the drive is healthy and still suits your needs, you can erase it, format it as APFS, and set it up again for encrypted Time Machine backups.
Erasing permanently deletes the drive’s contents, including its backup history. Recover anything you need that exists only in the old backup, such as a file you deleted from your Mac months ago.
While the backup is rebuilding, which could take several hours, you will be without a backup. If this is worrisome, you should consider getting a new drive (option #1 above) instead.
You have time to make the change carefully
Apple is providing substantial advance notice. You don’t need to buy a drive today, and the warning itself doesn’t mean your current backup has stopped working.
Over the coming year, check whether your backup is affected and choose a path: start fresh on a new SSD, or reformat a healthy existing drive. Either way, make sure you have a completed, encrypted APFS backup before upgrading to macOS 28 or finding yourself dependent on a replacement Mac that runs it.
If you’re unsure which drive to erase or how to preserve something in an older backup, I can help you work through the transition.
Further reading
