Guides / Before You Format the Drive

Before You Format the Drive

This is the last page on purpose. Erase is how you get a clean disk. It is also how you throw away the only copy of a folder you meant to keep. Copy first. Then pick a format that matches how you’ll actually use the thing.

About 8 minutes · Tick the steps as you go

1. Copy anything you still want

If it mounts, copy files to another disk before you touch Erase. If it doesn’t mount, try First Aid and a mount — and recovery software if the files matter — before you wipe it. I cannot get them back for you afterward.

If Finder can open it, copy the folders you care about to another drive. If it doesn’t mount, finish External Drive Won’t Mount first. Confirm the copy actually opens on the destination, not just that the progress bar finished.

Erase cannot be undone. There is no Trash for a formatted volume.

2. Pick a format on purpose

APFS is what I use for a Mac-only SSD. Mac OS Extended (Journaled) is the older Mac format — still fine for some spinning disks and older machines that never learned APFS.

exFAT is the practical choice when the same disk has to sit on a Windows PC. MS-DOS (FAT) is for small sticks (think 32 GB and under) and it nags you about long names. NTFS is a Windows format; don’t expect a Mac to write it after a casual erase in Disk Utility.

APFS — Mac SSDs, snapshots, the default I want for a disk that will only see macOS.
Mac OS Extended (Journaled) — older Macs, some mechanical drives.
exFAT — share with Windows, files larger than FAT will allow.
MS-DOS (FAT) — small cross-platform sticks. Volume names stay short (11 characters).

3. Scheme, then Erase

Show All Devices. Click the device — the outermost row, the hardware — not a leftover volume under it. If Scheme is missing from the Erase sheet, you clicked a volume. Go up one row.

On a Mac you bought this decade, Scheme should be GUID Partition Map. Then choose the format, type a name, and Erase. Secure-erase sliders are a spinning-disk leftover; they don’t show up for most SSDs, and they shouldn’t. For an SSD you care about locking, use encryption after it’s formatted, not a fake multi-pass wipe.

View > Show All Devices. Select the device (outermost row). Erase > Scheme: GUID Partition Map. Format: the one you picked above. Name: something you’ll recognise in Finder. Erase, wait, then copy a single test file on and off before you trust a full backup to it.

This is for a USB disk you own. If you meant to wipe a Mac you’re selling, that’s Erase Assistant / a full Mac erase — not this page.

4. If Erase fails

Try another cable and the enclosure’s power adapter, then Erase again. If Disk Utility still can’t finish, the enclosure or the drive is done. Formatting is not a repair for hardware that never enumerated cleanly.

Apple’s pages, if you want them: Erase and reformat a storage device

I wrote these lists from the same public Mac Help and Disk Utility notes everyone can read — in my own words, with the order I actually use. Apple’s pages are linked above if you want the official version.

Still stuck?

If this list didn’t get the drive back, write to me.

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