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macOS 10.13 support

We’re increasingly being asked about support for macOS 10.13. Normally, when a version of the macOS is in beta, our response is to comment that we won’t promise support until we’ve seen the final release, because we got our fingers burned many versions ago when Apple released some extra changes in the final build that weren’t in the beta. The upshot is that we don’t think it’s responsible behaviour to release a disk utility that hasn’t been properly tested with the final build, and that means that compatibility updates will typically come rather later for our software than for, say, a productivity application. Some of our customers, even having been told this over and over, still contact us about every single major release… we can’t fault their dedication, I suppose, but it’s unlikely that we’ll ever change our minds on this.

Now, in the case of macOS 10.13, there is a bigger problem. Apple is changing filesystem. In order for a low-level disk utility like iDefrag or iPartition to function, we need to know exactly how the filesystem organises data on disk; indeed, inside our products we have pretty comprehensive implementations of HFS+, FAT and NTFS. Apple’s new filesystem APFS, is a completely new design, and you’d have thought that Apple would give us disk utility vendors a fighting chance of getting up to speed before the release of 10.13 by releasing design documentation well in advance, but no, that hasn’t been the case this time around. The only documentation we have about the APFS volume format is this table. Yes, that document includes other information about what APFS can do, but it doesn’t include any detail of the on-disk data format other than a table comparing it to HFS+.

While it’s impossible to be certain, it’s highly likely that adding APFS support to our products, if/when Apple ever releases technical details of its volume format, will involve months of work, and since APFS is going to be the default format for many devices (specifically, anything that uses only Flash storage), as well as being an option for other situations, we simply can’t promise macOS 10.13 support right now. Even if the current version works just fine in many respects, we don’t think that’s sufficient to say that macOS 10.13 is supported, because of the sheer number of devices that will be using APFS.

We’ll add at this point that “upgrading” to APFS is not an optional step for Flash-only machines — it will happen automatically when you install macOS 10.13, and there is no way to “downgrade” again, short of backing up and reformatting your disk completely. This is similar to the way recent versions of the macOS “upgrade” your disk to use Core Storage without asking, only in that case you can manually “downgrade” again to plain HFS+ in a fairly straightforward manner.

TL;DR: We are not going to support macOS 10.13 at present.

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