Apple will remove support for encrypted Mac OS Extended (HFS+) volumes starting with macOS 28. This change means users with older encrypted external drives will need to decrypt or reformat them before upgrading to avoid losing access. Unencrypted HFS+ volumes will continue to be supported.

This move appears to be Apple's latest step in phasing out the HFS+ file system, which has been superseded by APFS (Apple File System) as the default since macOS High Sierra in 2017. APFS natively supports encryption and is designed for modern storage, including SSDs.

Apple suggests users back up data from affected drives, then either reformat them to APFS or decrypt them. Reformatting erases data but ensures compatibility. Decrypting preserves data but requires unlocking the drive with its password and can take considerable time for large volumes. This decryption process does not apply to encrypted Time Machine backups.