How to Avoid the APFS Conversion on macOS High Sierra

When you install macOS High Sierra with flash storage, that volume is automatically converted to the all-new APFS (Apple File System). Apple doesn’t require your consent: want it or not, the HFS+ volume is converted to APFS, a transition that you cannot stop – at least according to Apple. But there is one thing that the tech giant forgot about: the developer community, which always quickly reacts to this sort of news with a workaround. And so if you don’t want the SSD to be converted into APFS, there is a way to stop the process.

How to prevent automatic conversion to APFS

Use an external volume

Unpacking the macOS High Sierra installer will unveil many ‘secrets’ that Apple is hiding away from the average user, and the startosinstall is just one of them. This utility will help you skip the APFS conversion faster than the first method, since the command line you’ll enter into Terminal will instruct the installer to skip that specific step, eliminating the need to create a clone and move it to another drive. Follow the steps below:

After the upgrade is complete, you can always check whether the startup drive has been converted or not.

How to force APFS conversion

The startosinstall utility also allows you to force an APFS conversion, except for those storage disks that don’t support the new file system. As of writing, Fusion Drive doesn’t support APFS, but Apple says that this will change soon. You can convert your HDD to APFS, but it isn’t recommended because, as Apple highlighted during the keynote announcing the new file system, this system was designed for SSDs and not for HDDs.

Still, if you do want to take the step regardless – maybe you’ve changed your mind and now want to upgrade to the new file system – then you should follow these steps:

You’ll see Terminal copying the required files and, when done, it will restart your Mac and complete the macOS High Sierra installation, with the startup disk now converted to APFS.