We're at High Sierra beta 9, and it still doesn't seem possible to convert an HFS+ Journaled boot drive "in-place" to APFS.

I tested this with a totally fresh install using a late 2014 27" Retina iMac, installing onto an external SATA LaCie Thunderbolt 2 drive that I partitioned into three parts: 500GB for Sierra, 500GB for High Sierra, and 1TB for future use.

While I was able to install the latest High Sierra 10.13 Beta (17A360a) on one of the partitions, I could not get the option to convert that HFS+ Journaled partition into APFS.

Supposedly, it can be done "in place" by booting to the 10.13 Recovery partition, starting the Disk Utility, and using the menu options to "Convert to APFS". However, when I did that those options are grayed out when a partition containing an OS is selected. Interestingly, if the volume DOESN'T have an OS, then that option is available

Awfully hard to test our software on a new file system if I can't convert the boot drive to the new file system...

UPDATE: I was able to erase one of the external HDD partitions, reformat it to APFS, then install the High Sierra beta from the Recovery Partition. It installed, it booted, and it ran through its setup processes. For a very long time, it seemed it was doing something to the internal Fusion drives -- and I didn't see them mount on the desktop, but I think maybe Spotlight was trying to index them. During this time, neither Safari nor System Preferences would open ("Application could not be opened)". However, eventually, things settled down and I was able to eject my internal Fusion drive, and I was able to do things again. So we'll see.

  • Something I saw recently makes me wonder if maybe only ssd drives are going to apfs support.apple.com/en-ca/HT208018 Commented Sep 9, 2017 at 9:39
  • Is there any notion as to WHY there is this special affinity for SSD drives? The benefits of APFS seem to go way beyond HFS+ Journaled, even for a traditional HDD. Commented Sep 9, 2017 at 18:05
  • Only SSD boot drives get automatically converted to APFS in the final release. The documentation I saw says it won't convert fusion drives by default.
    – CyberSkull
    Commented Sep 28, 2017 at 5:53
  • @CyberSkull: not necessarily. Check out the sob story at apple.stackexchange.com/questions/333045/…
    – WGroleau
    Commented Nov 28, 2018 at 22:46

3 Answers 3


Awfully hard to test our software on a new file system if I can't convert the boot drive to the new file system

Since you have space to spare: convert an empty partition to APFS, then install 10.13 on the APFS partition. Or use SuperDuper or somesuch to copy your existing 10.13 installation to the new partition.

  • 1
    So having an APFS boot drive is NOT problematic for an HDD? It's just the in-place conversion that is causing headaches? Commented Sep 9, 2017 at 18:08
  • 1
    Sorry, missed the fact you were talking about an HDD. HDD could be problematic for now, Apple has given priority to SSD: apple.stackexchange.com/questions/294137/…
    – Hobbes
    Commented Sep 9, 2017 at 18:38
  • 1
    See my "UPDATE" in the original posting. Commented Sep 9, 2017 at 21:40

I converted the hard drive in my iMac (no SSD) to APFS. I had to back everything up and erase the drive, reformatting it to APFS from the network recovery Disk Utility, and then from that install High Sierra. None of this went well from the Recovery Partition.


It is possible from recovery mode. Start the mac in recovery mode (hold cmd+R at boot). Open disk utility, select volume from the left click Edit and convert to APFS. If option is greyed out unmount the volume first from the toolbar.

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