Apple has confirmed an important storage compatibility change that will affect some Mac users when macOS 28 arrives next year. If you still use an encrypted Mac OS Extended, also known as HFS+, volume on an external drive or another storage device, you will need to decrypt or reformat it before upgrading. Otherwise, macOS 28 will no longer support that encrypted volume, which means you won’t be able to continue using it with the new operating system.
The change only applies to encrypted Mac OS Extended volumes. If your HFS+ drive isn’t encrypted, Apple says it will continue to work with macOS 28 and later. This move continues Apple’s long transition to the Apple File System (APFS), which became the default file system for Macs with macOS High Sierra and already includes built-in encryption support.
Apple explained the change in a newly published support document, where the company confirmed that macOS 28 will only support Mac OS Extended volumes if they are not encrypted.
“In macOS 28 and later, the Mac OS Extended file system format will be supported only for volumes (disks and other storage devices) that aren’t encrypted. For future macOS compatibility, either decrypt or reformat any encrypted Mac OS Extended volumes.”
Apple also says Macs running macOS 26 or later can notify users when they connect an affected encrypted HFS+ volume. The notification identifies the drive by name, giving users enough time to prepare before upgrading to macOS 28. If you don’t receive a notification but still want to verify your drive, you can check its format and encryption status manually in Disk Utility. If the volume shows both Mac OS Extended and Encrypted, it won’t remain compatible after installing macOS 28.
How to keep your drive compatible with macOS 28
Apple recommends backing up everything stored on the affected drive before making any changes. Once your data is safe, you can either reformat the drive using APFS or decrypt the existing volume. Reformatting permanently erases all data, while decrypting lets you continue using the drive and even convert it to APFS later without deleting its contents.
How to check and update your encrypted HFS+ volume
• Open Disk Utility from the Utilities folder or search for it with Spotlight.
• Choose View > Show Only Volumes.
• Select the volume in the sidebar and check the information below its name. If it shows Mac OS Extended and Encrypted, the volume won’t work with macOS 28.
• Back up any important files before making changes.
• Either erase and reformat the volume using APFS or APFS (Encrypted), or decrypt the existing volume by unlocking the drive, Control-clicking its icon, and selecting Decrypt.
• After decryption finishes, you can open Disk Utility, choose Edit > Convert to APFS, and convert the volume without erasing it. If you still want encryption, you can encrypt the APFS volume afterward.
Apple also notes that this decryption option doesn’t apply to encrypted Time Machine backup disks, so users who rely on those drives should plan accordingly before upgrading. Large encrypted volumes can also take a considerable amount of time to decrypt, so completing the process well before installing macOS 28 is a good idea.
Although Apple didn’t explain why it removed support for encrypted HFS+ volumes, the decision aligns with its long-term focus on APFS as the standard file system across modern Macs. Users who still depend on older encrypted HFS+ drives now have plenty of time to back up their data, switch to APFS, and avoid compatibility issues before macOS 28 becomes available.
