Apple has published a new support document that should alert owners of older external hard drives. Starting with macOS 28, Macs only support the aging Mac OS Extended file system in unencrypted form – anyone using an encrypted HFS+ drive must take action before updating, otherwise it will no longer be mountable.
In a support document published on July 7, Apple announced that macOS 28 and later versions will only support the Mac OS Extended file system format for unencrypted volumes. This primarily affects older encrypted external drives, which will need to be either decrypted or reformatted before upgrading to the upcoming system. This move is part of Apple's ongoing modernization of the Mac platform, which, with macOS Golden Gate, will rely exclusively on Apple Silicon for the first time, definitively leaving the Intel era behind. Since APFS has been the standard Mac file system since 2017, this announcement appears to be another step in the gradual replacement of the older format.
What's changing with macOS 28
The core of the announcement is narrowly defined: Mac OS Extended – also known as HFS Plus or HFS+ – will remain usable in macOS 28 and later, but only for unencrypted volumes. Encrypted HFS+ volumes will no longer be mounted by the Mac unless the user actively changes the setting beforehand. Apple hasn't given a specific reason. Since APFS natively supports encryption and has been the default since macOS High Sierra 2017, this move suggests that Apple is phasing out the older format in the long term.
Important for context: This is not a blanket end for HFS+. Unencrypted Mac OS Extended Volumes will continue to work under macOS 28, and APFS drives are not affected by the change anyway.
Who is affected – and who is not
This only affects users of drives that are both in Mac OS Extended format and encrypted. In practice, this most likely applies to older, password-protected external hard drives that have served as archives over the years. Apple explicitly points out that the decryption method described below does not apply to encrypted Time Machine backup volumes – such backup drives must therefore be handled separately.
To prevent anyone from being caught unprepared during the update, Macs starting with macOS 26 will display a notification as soon as they detect an encrypted Mac OS Extended drive that will no longer be compatible with macOS 28. The message will identify the affected volume directly by name.
This is how you can check the status of a drive
If you're unsure whether a drive is affected, you can find the answer in Disk Utility. In the "View" menu, select "Show Volumes Only," then select the desired volume in the sidebar and read the format information directly below its name. If both "Mac OS Extended" and "Encrypted" appear there - for example, in the form CoreStorage Logical Volume • Mac OS Extended (Case-sensitive, Journaled, Encrypted) - the drive is no longer compatible with macOS 28.
Two ways to save the drive
In both cases, it is recommended to back up all data that should be retained beforehand. After that, two options are available.
The first option is reformatting: The volume is erased and recreated in APFS or APFS (encrypted) format. This permanently removes all data but ensures that the drive will work with future macOS versions.
The second method is decryption, which preserves the existing data. To do this, connect the drive, unlock it with the encryption password, and then, in Finder or on the desktop, Control-click and select "Decrypt." After re-entering the password, the process begins, which can take some time for large volumes; the progress is displayed using the command diskutil cs list in Terminal. Once decryption is complete, the volume can optionally be converted to APFS using Disk Utility without data loss, and then re-encrypted if needed.
The slow end of HFS+
With the removal of HFS+ encryption, Apple continues the gradual phasing out of a file system that dates back to the late nineties. APFS has long since replaced the format on internal storage; external drives are the last major area where HFS+ is still widely used. macOS 28 is expected to be released this fall – leaving plenty of time to back up and migrate affected archives before facing an unreadable drive later. (Image: Shutterstock / Yalcin Sonat)
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