Mac users with encrypted external drives formatted in the older HFS+ standard need to act before macOS 28 arrives, or those drives will stop working entirely with their Mac.
Apple published a support document confirming that macOS 28 will refuse to mount any encrypted Mac OS Extended volume, also known as HFS+ or HFS Plus.
The change does not affect unencrypted HFS+ drives. Apple has confirmed those will continue to work in macOS 28 and beyond.
The issue is specific to drives where encryption was enabled on top of the older format, which was a common choice for people protecting external backup drives and long-term archives before APFS became the default in 2017.
How to Find Out If Your Drive Is Affected
Open Disk Utility, select a drive, and check the format label beneath its name. If the description includes both “Mac OS Extended” and “Encrypted,” that drive will not work after upgrading to macOS 28.
Apple says macOS 26 will also begin proactively flagging these drives, showing a notification that identifies the affected volume by name before the incompatibility becomes a real problem.
Two Ways to Keep Your Data
Users who want to preserve their existing files without reformatting can decrypt the drive while staying on a current version of macOS.
Connect the drive, unlock it with its encryption password, then Control-click its icon in Finder and select Decrypt.
Apple notes that decryption can take a long time on large drives, and progress is visible through Terminal. Once complete, the drive can optionally be converted to APFS through Disk Utility without erasing the data.
The other path is reformatting. That means backing up all files first, then erasing the volume and setting it up fresh as APFS or APFS (Encrypted) through Disk Utility.
The drive will work normally in all future versions of macOS, but the reformat permanently deletes whatever was on it beforehand.
Apple has not explained its reasoning for the change. APFS has supported native encryption since macOS High Sierra in 2017, and dropping the encrypted variant of the older format follows a broader pattern of Apple nudging users away from HFS+ over time.
Notably, encrypted Time Machine backup disks are excluded from the decryption workaround, so anyone using an encrypted HFS+ Time Machine drive will need to reformat and start a new backup set.
Anyone with older encrypted drives sitting in a drawer, storing tax records, family photos, or archived projects, should connect them and check the format before upgrading. Waiting until after macOS 28 installs removes the option to decrypt in place and recover the data without a separate older Mac.
