One of my favorite Mac apps, DiskWarrior, has been waiting for the APFS format documentation (also called the APFS volume specification) for a while, in order to make a new program version which can rebuild APFS disks. Recently, according their page linked above, this documentation was released and Alsoft is using it to update DiskWarrior. I would like to look at this documentation myself, as I find it interesting. However, I can't find the documentation anywhere. I've found a few documents like this, but I don't think that's what I'm looking for, since that document is not as comprehensive as what I would expect from a full volume format specification.

Do I need a certain Apple subscription to see this documentation or am I simply failing at googling for it?


2 Answers 2


I think Alsoft's use of the phrase APFS format documentation is just that - a phrase they've used rather than referencing an official title.

The Apple File System Reference is almost certainly what they're referring to. This reference was publicly released on 17 September 2018, and Alsoft made that statement on 4 October 2018.

Prior to the Apple File System Reference, there was no consolidated documentation from Apple regarding APFS - at least not to this level of detail. In fact, the most comprehensive documentation until this was released was actually the result of private academic work in the computer forensics field.

As for Apple itself, we've had the following documentation:

However, the Apple File System Reference was last updated in February 2019 June 2020.

  • I guess I was wrong. I came across that document (as I said above) and I thought it wasn't it, but apparently it is. Thanks for the info and the list of the documentation concerning APFS thus far.
    – GDP2
    Commented Jul 23, 2019 at 0:05

Apple has not yet published full APFS documentation. Only information about reading APFS disks has been released. Missing documentation is about how to write to APFS disks. Until then, DiskWarrior 6 to rebuild APFS disk directory cannot be released.

Check out what Micromat says about it in relation to TechTool Pro:

APFS - AGAIN no support

Providing full support for APFS is entirely dependent on Apple releasing the required documentation for developers. So far, only the documentation explaining the APIs for reading APFS volumes has been released. It is about 140 pages long. We need similar documentation for writing to APFS volumes.

source: https://www.micromat.com/component/kunena/techtool-pro-11/5225-apfs-again-no-support

Why? When will it happen? Surprisingly, APFS is still a work in progress. We could say that it is still in beta phase. Hopefully, Apple will announce Time Machine 2 supporting APFS on June 2020 (WWDC). Then, macOS 10.16 with it will be released by end of September 2020. And then Apple will hopefully release really and truly full (sort of) APFS documentation. Then DiskWarrior 6 could be expected in about three to six months testing period. Hopefully.

  • Thanks for the info. I find it strange that Micromat is saying this, yet Alsoft is moving forward with their implementation of APFS disk-rebuilding. The documentation available is sufficient for their application, according to their page. Is it possible that Alsoft has access to some documentation which isn't available to others?
    – GDP2
    Commented Jul 23, 2019 at 0:08
  • Only Apple has such documentation, yet it is a moving target and thus not released yet.Prosoft Engineering acknowledges it for Drive Genius: Repartition, and Rebuild utilities are not supported on APFS
    – StaX
    Commented Jul 23, 2019 at 11:34
  • With all due respect, this web form is hard to use. First, I cannot paste all text at once. Second, no way to edit after a few minutes. So, here it goes in several parts. Frustrating!
    – StaX
    Commented Jul 23, 2019 at 11:48
  • 2
    In other words, Apple --the richest company on planet Earth with enourmous resources-- is more bussy making emojis or toying with iOS toys instead of devoting required resources to improve macOS (the real computer!) in proper time. Do not get me wrong. I love Apple and macOS, but this situation is unacceptable for customers that use Macs to work, developers that live from their work and Apple itself as a prestigious corporation! Hopefully, things will change for the better soon. Maybe within this year; most likely next year after WWDC June 2020 as said. Hopefully!!!
    – StaX
    Commented Jul 24, 2019 at 6:47
  • 1
    Yes, I've felt the same way many times. Apple needs to devote more attention to things like the filesystem and the kernel, making these things more accessible to developers and power-users who need such access. But sadly you're very right. Hopefully things change indeed!
    – GDP2
    Commented Jul 24, 2019 at 15:26

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