Since macOS 10.13 High Sierra, the default file system for Mac computers with solid-state drives is the Apple File System or APFS. This new file system features encryption, space sharing, snapshots (thanks to the copy-on-write technology), fast directory sizing, and much more. But as of writing APFS does not currently support either traditional hard disk drives (HDDs) or external drives, and so macOS has to support other system file formats in order to read and write to and from other drives.
APFS File System Formats
Having APFS on board brings a handful of advantages, such as support for multiple volumes and space sharing. Each volume added to the APFS container (or partition) can have its own format, and Apple provides a few options for this in Disk Utility:
- APFS: The Apple File System format for volumes using macOS High Sierra.
- APFS (Encrypted): Encrypts the Apple File System formatted partition.
- APFS (Case-sensitive): The volume is case-sensitive to file and folder names. For example, folders named “bestreviews” and “BESTREVIEWS” are classed as two different folders.
- APFS (Case-sensitive and Encrypted): The volume is both case-sensitive to file and folder names, and encrypted.
Other File System Formats Available in Disk Utility
In some cases – for example, when installing Windows onto a Mac – you might need to partition the startup disk to apply a different file format. To stick with our example, you may already know that Windows supports neither the APFS nor the older HFS+ file formats, so you will need to use a file format on the dedicated partition that is readable by the operating system – in this case FAT or ExFAT.
Or, if you would just prefer to not be a guinea pig for Apple’s grandiose APFS experiment, you can either prevent High Sierra from converting the startup disk to APFS or add another partition that uses the legacy Mac OS Extended (Journaled) file format. The latter will allow you to keep the APFS (and see how it works) and still enjoy the legacy file format, which might make you feel a little more comfortable with the change.
As for external drives, that can be used in three main file formats: Mac OS Extended, MS-DOS (FAT), and ExFAT.
To partition an internal or external drive, follow the steps below:
- Launch Disk Utility and select the drive in the sidebar, then click on the “Partition” button.
- A prompt will appear informing you about the space sharing option that APFS volumes provide, but click on the “Partition” option.
- Click on the + button to add a new partition.
- The volumes are displayed in a pie chart. Enter a name for them on the right, and select the desired file format:
- Mac OS Extended (Journaled): The legacy file system format (Journaled HFS Plus) that Apple used on macOS 10.12 Sierra and earlier.
- Mac OS Extended (Journaled and Encrypted): The legacy file format, but that also encrypts the partition and requires a password.
- Mac OS Extended (Case-sensitive and Journaled): The legacy file system format that is case-sensitive to file and folder names.
- Mac OS Extended (Case-sensitive, Journaled, and Encrypted): The legacy file format that is case sensitive for file and folder names, requires a password, and encrypts the partition.
- MS-DOS (FAT): The file format used for Windows volumes smaller than 32GB.
- ExFAT: The file format used for Windows volumes larger than 32GB.
An important step to consider when partitioning the drive is to click on the View > Show All Devices in Disk Utility, otherwise you won't see all the available volumes and partition mapping options. Apple has hidden the map scheme option by default, and without selecting a partition map you won't be able to format the targeted drive.
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