Apple has confirmed that macOS 28, due in 2027, will stop supporting encrypted Mac OS Extended volumes. If that sentence means nothing to you, you are almost certainly fine. If it made your stomach drop, this one is for you.
The short version: an old external drive you encrypted years ago could become unreadable the moment you install macOS 28. The good news is that there is plenty of warning, and a fix that does not involve losing anything, as long as you act before you upgrade.
What Is Actually Changing
Mac OS Extended, also known as HFS+, is the file system Apple used on Macs for the best part of two decades before APFS took over as the default back in 2017. Plenty of older drives are still formatted with it.
Here is the important nuance. macOS 28 is not killing HFS+ outright. Unencrypted Mac OS Extended drives will keep working exactly as they do now. It is specifically the encrypted version of the format that Apple is dropping. If you ever right clicked a drive and chose to encrypt it, or set one up as an encrypted backup, that is the one at risk.
Who This Actually Hits
Not many people, honestly. If your drives are recent, or you have already moved to APFS, there is nothing here to worry about.
The ones who need to pay attention are the long term Mac owners with a drawer full of history. Old encrypted Time Machine disks. An archived project drive you locked down and forgot about. The external you have been dragging from Mac to Mac since 2015. If any of those were encrypted under the old format, macOS 28 will refuse to read them, and you will not find out until the data is already stuck behind an OS that cannot open it.
What to Do Before You Upgrade
You have two clean options, and both are far easier than a data recovery job later.
The simplest is to decrypt the drive. In Finder, right click the volume and choose to turn encryption off. Your files stay exactly where they are, the drive stays HFS+, and it drops off the endangered list entirely. It just will not be encrypted any more, so only do this on a drive that does not need locking down.
The better long term move is to convert to APFS, Apple’s modern format, which supports encryption properly and is where everything is heading anyway. The catch is that reformatting erases the drive, so the order matters: copy the data off first, reformat to APFS, then copy it back. Do not reformat a drive that is your only copy of something.
Either way, the key is timing. Do it while you are still on a version of macOS that can read the drive. Apple is expected to start throwing up compatibility warnings in macOS 26, so treat those as your cue rather than something to click past.
The Bigger Pattern
None of this is Apple being malicious. It is the same housekeeping that saw it call time on the Intel era and, more recently, pull the plug on restoring ancient iPhones. Apple retires the old world in small, quiet steps, and every so often one of those steps lands on someone still using the thing being retired.
Encrypted HFS+ is this year’s step. You have until 2027 and a very simple fix. The only real mistake here is finding out about it after you have already hit upgrade.
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