How to Format an External Drive on Mac (APFS vs ExFAT)

Formatting a drive on a Mac is a two-minute job in Disk Utility — the real decision is which file system to pick, and the classic mistake is erasing the volume instead of the whole device. This guide handles both: the format choice in plain terms, then the exact click path.

Before anything: this erases the drive

Formatting (Disk Utility calls it erasing) destroys every file on the drive, and there is no undo. Copy off anything you might want — including files in hidden folders other machines may have written — before you open Disk Utility. If the drive currently holds the only copy of anything, stop and back it up first. Done? Continue.

Pick the right format

• APFS — the modern Mac-native format, and the right answer for any drive that will only be used with Macs, especially SSDs. You get snapshots, fast copies, and optional strong encryption (APFS (Encrypted)). Time Machine backup drives on current macOS use APFS. Windows cannot read it without extra software.
• exFAT — the cross-platform choice. Reads and writes natively on macOS, Windows, game consoles, and most TVs and cameras. No encryption, no snapshots, less resilient to yanked cables — but if the drive moves between a Mac and anything else, this is the one. (Avoid MS-DOS/FAT32 unless a device demands it; it caps files at 4 GB.)
• Mac OS Extended (Journaled) — the pre-2017 Mac format, also called HFS+. Choose it only for drives that must work with very old Macs (macOS 10.12 and earlier). For everything else APFS has replaced it; on spinning hard drives both work, and APFS remains the simpler default on Ventura, Sonoma, and Sequoia.

Shorthand: Mac-only → APFS. Mac + anything else → exFAT. Museum-grade Mac → Mac OS Extended.

Erase the drive in Disk Utility

1. Open Disk Utility (Applications → Utilities, or find it with Spotlight).
2. Choose View → Show All Devices. This is the step everyone skips: without it the sidebar shows only volumes, and erasing a volume leaves the old partition table in place.
3. In the sidebar, select the drive's top-level device — the un-indented entry with the manufacturer name — not the indented volume beneath it.
4. Click Erase in the toolbar.
5. Enter a Name, choose your Format, and set Scheme to GUID Partition Map. (The Scheme menu only appears when a whole device is selected — if you do not see it, go back to step 3.)
6. Click Erase and wait. The freshly formatted drive mounts automatically when it finishes.

Choosing APFS actually creates an APFS container with one volume inside — that is normal, and you can add more volumes later that share the free space.

If the erase fails

Two common failures. "Couldn't unmount disk" usually means something is using the drive — close Finder windows and apps touching it, then retry (see our guide to disks that claim to be in use). Repeated failures partway through an erase, especially on an older spinning drive, are a health warning sign: run First Aid, and if errors persist, stop trusting the hardware with anything important. For scripted or stubborn cases, the command-line equivalent is diskutil, covered in our diskutil guide.