Disk Utility’s format menu is worth a look before you erase a drive. The right choice depends on where you’ll use it: a current Mac, an older Mac, or a Windows computer.
For most Mac-only drives, choose APFS. Mac OS Extended (Journaled), also called HFS+, is mainly for older Macs and software that requires it. Choose exFAT when you need to move files between macOS and Windows.
Which disk format fits your drive?
| What you’ll use the drive for | Choose |
|---|---|
| A modern Mac’s startup disk | APFS |
| An external SSD or hard drive used only with modern Macs | APFS |
| A drive shared with a Mac running macOS Sierra or earlier | Mac OS Extended (Journaled) |
| A drive required by older Mac backup or cloning software | The format that software specifies, often Mac OS Extended |
| File transfers between current Macs and Windows computers | exFAT |
| A new Time Machine backup on current macOS | Let Time Machine set up the disk; APFS is generally preferred |
Your Mac’s internal startup disk already uses the format macOS needs. Leave it alone unless you’re deliberately reinstalling macOS or following a recovery procedure.
Why APFS is the Mac default
APFS is Apple’s file system for macOS High Sierra 10.13 and later. It’s optimized for flash storage, so it’s an easy recommendation for an external SSD. Apple also supports it on traditional hard drives, though its speed benefits are generally more noticeable on SSDs.
APFS supports encryption, snapshots, and multiple volumes that share free space within one container. That last feature is clever: you can give projects separate volumes without deciding in advance how much space each gets. Apple’s guide to file system formats explains the available options.
The catch is compatibility. A Mac running macOS Sierra or earlier can’t natively use an APFS drive. Windows can’t natively read and write APFS drives either.
Add an APFS volume without erasing the disk
If your drive already has an APFS container, you can add a volume that shares its available space:
- Open Disk Utility and choose View > Show All Devices.
- Select an existing APFS volume in the sidebar.
- Choose Edit > Add APFS Volume, or use the Add Volume button.
- Name the volume, choose an APFS format, and click Add.
This works nicely when you want separate storage areas on one drive. If you need a fixed division of disk space, use partitions instead. Apple’s APFS volume instructions also cover optional size limits.
When Mac OS Extended still makes sense
Choose Mac OS Extended (Journaled) if the drive must work with a Mac running macOS Sierra or earlier. It’s also the right choice when a legacy app, disk utility, or cloning workflow specifically requires HFS+.
A portable hard drive doesn’t need HFS+ merely because it has spinning platters. APFS works on hard drives, too. Compatibility is the stronger reason to pick HFS+.
What about Time Machine?
For a new Time Machine backup on current macOS, let Time Machine guide the disk setup. APFS is generally preferred for new backup disks. Keep in mind that Time Machine reserves the entire APFS backup volume for backups. To store other files on the same drive, use Disk Utility to add a separate APFS volume. An existing backup disk or an older Mac workflow may use Mac OS Extended, so check the requirements before erasing a working backup.
Use exFAT for Mac and Windows file transfers
exFAT lets current macOS and Windows computers read and write the same removable drive without a third-party file-system driver. It’s a practical choice for documents, photos, and large video files that travel between the two.
The trade-off is that exFAT lacks APFS features such as snapshots and shared-space volumes. Don’t use it for a Mac startup disk or a drive that needs Mac-specific backup features. If the computers stay in one place, a network share or cloud storage service can be more convenient than carrying a drive between them.
How to format an external drive in Disk Utility
Erasing a drive deletes its files. Copy anything you need elsewhere and check that the copy opens before continuing.
- Connect the drive and open Applications > Utilities > Disk Utility.
- Choose View > Show All Devices.
- Select the physical drive at the top of its group in the sidebar, then click Erase.
- Enter a name. Choose GUID Partition Map for normal use with modern Macs.
- Choose APFS for Mac-only use, Mac OS Extended (Journaled) for older-Mac compatibility, or exFAT for Mac and Windows file transfers.
- Click Erase, then Done.
If Scheme doesn’t appear, you’ve probably selected a volume beneath the drive. Select the top-level physical device and try again. Apple’s Disk Utility erase guide shows the device hierarchy.
A drive that opens on your Mac but won’t accept files may be formatted as NTFS. macOS can generally read NTFS but doesn’t natively write to it. Check the drive’s format in Finder with Cmd + I before deciding whether to copy its files elsewhere and reformat it.
For a new Mac-only drive, I recommend APFS. Its shared volumes are genuinely handy, and you can choose an encrypted APFS format when the drive holds sensitive files (keep the password somewhere safe). HFS+ earns its place with older Macs; exFAT handles the drive you share with Windows.