APFS or Mac OS Extended, what actually changed

APFS replaced Mac OS Extended as the Mac default in 2017. It brought space sharing, snapshots, cloning and built in encryption, all designed around flash storage. Mac OS Extended still exists, still mounts and still has jobs left, but macOS 28 removes support for the encrypted version of it.

Disk Utility offers you both and explains neither. What follows is what actually changed between them, plus the short list of cases where the older one is still the right answer.

The two formats, side by side

The verdict in one line. On any Mac made this decade with internal flash storage, APFS is not a choice you make. It is what macOS installs on. There is no supported way back.

How each of those mechanisms actually works is a longer subject on its own. This page stays on what separates the two.

Why the two do not rank cleanly

Read the table as one decision rather than ten. The two formats target different hardware. Every row follows from that.

Where a moving head made seeking expensive, keeping metadata in one fixed place and overwriting blocks where they sat were the right calls. Where any block costs the same to reach, neither call buys anything. Both get in the way of features worth having instead.

So the honest comparison is not a scoreboard. It is a question about the drive underneath. That is why the rest of this page is organised by the case you are in rather than by which format is better. It is also why the history behind the decision stays where it belongs, in the file system pillar.

On flash it wins. On a spinning disk it does not

This is the part every comparison skips. It is also the only performance question worth asking.

APFS writes changed data to new blocks rather than over the old ones. It also scatters file metadata alongside file data instead of keeping it in one fixed place. On a solid-state drive, where any block costs the same to reach as any other, neither choice costs anything.

On a spinning platter both cost real time. Scattered metadata means the head travels for a directory listing that Mac OS Extended answers from one location. Copy on write fragments a disk that has no cheap way to be defragmented. Reports of sluggish behaviour and slow folder listings on APFS hard drives have followed the format since it arrived.

Mac OS Extended keeps its metadata in a fixed location, which is exactly the design a moving head wants. On a hard disk it still holds up better.

Fusion Drives, where Apple hesitated

The clearest evidence that Apple knew this is what happened to Fusion Drives.

When High Sierra shipped in 2017 it converted internal drives to APFS automatically and gave nobody a choice. Apple's own compatibility note carried one exception, stated plainly. Fusion Drives and hard disk drives were not converted.

Fusion Drives had been converted during the beta, then the support was pulled before release. Anyone who had already been switched had to reformat back. APFS support for Fusion Drives arrived a year later with Mojave.

What the change looks like from Finder

Most of the table above is invisible until something makes it visible.

Free space stops being a fixed number. Every volume in an APFS container reports what is left of the shared pool, so two volumes on the same drive show the same figure and both move while you watch.

Duplicating a large file becomes instant, then costs nothing on disk, because the copy points at the same blocks until one of them changes. Finder still reports the full size for each. Neither figure is wrong.

Deleted space stops coming back on demand, because a snapshot can hold blocks the live volume has already released.

None of that happened under Mac OS Extended, where a volume had a size, a copy was a copy and a delete was a delete. People who learned Mac storage on the old format are not misremembering. The rules changed underneath them.

Which version of macOS reads which

The middle row catches people. From Mojave onward a Mac cannot start from a Mac OS Extended volume, though it reads one perfectly well as ordinary storage.

Time Machine, the exception that lasted three years

APFS became the Mac default in 2017. Time Machine went on demanding Mac OS Extended until 2020.

The reason was specific. Time Machine backups rely on hard linked folders, a trick Apple built into HFS+ for exactly that purpose. Early APFS had no equivalent. macOS 11 Big Sur added the missing piece and Time Machine could write to APFS at last.

Apple now names APFS the preferred format for a backup disk. Mac OS Extended backups still work, so an existing drive keeps going untouched. Apple says so on the same page.

There is no upgrade path. A Mac OS Extended Time Machine volume cannot be converted to APFS. Reformatting means erasing the backup history. An APFS Time Machine volume cannot be read by macOS Catalina or anything older.

When Mac OS Extended is still the right answer

Three cases, each narrower every year.

A Mac too old for APFS. Anything on macOS Sierra or earlier reads nothing else.

A spinning disk used for bulk storage. The metadata argument above has not gone away. Fixed location beats scattered on a platter.

An existing Time Machine drive with history worth keeping. It keeps working. Converting it means starting the chain again.

Everything else has drifted the other way. That drift has a date on it now.

The change that narrows it further

In July 2026 Apple published a support note about macOS 28. From that release, Mac OS Extended will be supported only on volumes that are not encrypted.

Unencrypted Mac OS Extended volumes carry on exactly as before, which Apple states directly. An encrypted one simply will not mount. Apple's guidance is to decrypt it or reformat it before upgrading. macOS 26 has been showing warnings about affected drives already.

Encrypted Time Machine backup disks sit outside that instruction and follow their own rules.

Read alongside everything above, the direction is not subtle. Apple has spent nine years moving one thing at a time out of Mac OS Extended. The encrypted case is the latest to go.

So which one

For the internal disk of any current Mac there is nothing to decide. APFS is what macOS installs on and what it boots from.

For a hard disk holding bulk data on a machine you control, unencrypted Mac OS Extended remains defensible on the metadata argument alone. macOS 28 leaves that case untouched.

For anything you plug in, the question stops being a two format comparison, because exFAT and the Windows formats enter the picture and the answer turns on what else has to read the drive. That is a decision with its own set of rows.