Apple in June announced that macOS High Sierra will come with the new Apple File System (APFS) on all supported Macs following its debut on iOS, watchOS and tvOS last year.

It’ll replace the dated HFS+ and users won’t be able to opt-out of the transition to APFS, according to a new support document for system administrator that was published recently on Apple’s website, as first noted Wednesday by The Loop’s Dave Mark.

APFS is the default file system in macOS High Sierra for Mac computers with all flash storage.

This is what happens when you upgrade to macOS High Sierra:

  • Mac computers with all flash storage are converted automatically (you cannot opt out)
  • Mac computers with hard disk drives and Fusion drives won’t be converted to APFS

If your Mac is using CPU-intensive FileVault encryption, those volumes will be converted from HFS+ to APFS just like unencrypted ones. The document also outlines APFS compatibility:

  • Devices formatted as HFS+ can be read and written to by devices formatted as APFS
  • Devices formatted as APFS can be read and written to by:
    • Other APFS-formatted devices
    • HFS+ formatted devices running macOS 10.12.6 or later

For example, a USB device formatted as APFS can be read by a Mac running macOS High Sierra, but not by a Mac running OS X El Capitan or earlier.

If you use Windows on your Mac desktop or notebook via Boot Camp, you won’t see any changes after upgrading to macOS High Sierra unless your Boot Camp volume is greater than three terabytes and resides on a Fusion Drive. That’s because Boot Camp in macOS High Sierra doesn’t yet support read/write operations to APFS-formatted Mac volumes.

If you use macOS’s File Sharing feature, keep in mind that APFS-formatted volumes don’t support share points over the network using the Apple Filing Protocol (AFP). SMB and NFS shares are supported when using APFS, according to the support document.

The option to enforce only SMB-encrypted share points is also available.

“After you upgrade your Mac and convert to APFS, you won’t need to make any changes to Time Machine settings,” Apple notes. “Any Time Machine share points must be shared over SMB instead of AFP.”

APFS is designed to make transferring files from one place to another faster.

Whether you’re transferring files to an external device or to another folder on your Mac, the speed differences is going to be very noticeable. Certain operations such as duplicating a file or getting a folder’s size are practically instantaneous.

For example, duplicating a 1-gigabyte file happens as soon as you choose the Duplicate command in the Finder. In addition to performance improvements, APFS arguably has better security, too, giving you more peace of mind in transferring files from one device to another.

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APFS has been written from scratch and is optimized for fast flash storage performance.

Not only does it feature built-in encryption, but supports a number of advanced features such as copy-on-write metadata, space sharing, cloning for files and directories, snapshots, fast directory sizing, atomic safe-save primitives and improved file system fundamentals.

Are you looking forward to transitioning your Mac to APFS this fall?

  • Ray

    Copies on the same drive are instantaneous because the data isn’t actually coped it’s just, basically, symbolically linked. It doesn’t matter if it’s 1gb or 18gb. This “performance boost” is not achievable when copying betweeen drives.

  • Cones1r

    I have the MBP from last year with touch bar. Will mine be converted?

    • pauleebe


    • Mr_Coldharbour

      If your Mac has a SSD and is able to run OS High Sierra, then yes it will be.

  • Jurassic

    Running the current beta of macOS High Sierra on an iMac with internal SSD. The transition to APFS was totally seamless (ZERO problems in using the new file system), and opening apps and files does seem a bit snappier than before.

    • usmc5939

      Did you have FileVault enabled before the switch to APFS? If so, was it still enabled after the upgrade? What will happen to users who don’t have FileVault turned on, will it enable APFS’s encryption on the drive? I’m still unclear as to the differences between the two, and what would happen differently with upgrading one that is already FV enabled and one that is not.

  • Rick Hart

    Will and Mac that I swapped out the regular drive for a ssd be changed


    My MacBook Pro (early 11) came with a HDD but I switched it to a SSD. Will it convert anyway if I update to High Sierra?

  • Darko

    I still don’t understand if a Fusion drive setup can be formatted (from scratch) to APFS. Clearly it will not be upgrade.
    But does APFS support Fusion drives???
    And will Time Machine work with a USB drive formatted in APFS? Or it will take Apple x months/years before they move from Hard links to something more modern and faster…

  • Maik Lohse

    So if I have a Fusion Drive (which I do) – should I not even bother switching to APFS?

  • ron_goodman

    I don’t understand why Apple has removed support for APFS on Fusion drives in the GM after supporting it in the Public Betas all summer. My iMac has been working fine. Why do I need to back-track to HFS+ at this late date, just to convert it back at some later date? I can understand not making the conversion the default yet for various reasons.

  • If you have a fusion drive and update to high Sierra, you cannot use bootcamp to install windows. It is a known issue by apple. Just for the moment.

  • Oliver Wetmore

    I have a Macbook pro mid 2012 with a non-native SSD. High Sierra failed to install with SSD formatted to APFS, it would kick out to the hard disk utility screen after a few minutes. After 3 attempts at this I changed the format back to the journal system and it installed normally. The SSD is about 3 years old now, would a newer one work with APFS?