Real screenshot · MacBook Pro, macOS 26In short
Back up anything on the drive first, because formatting erases it. Open Disk Utility, choose View, Show All Devices, select the drive at the top level, click Erase, choose a format and click Erase.
You plug in a drive, drag a file across, and the Mac will not take it. A new drive, or one used with Windows before, often needs formatting before a Mac can write to it. The right format depends on where you will use the drive.
The pictures are screenshots of Disk Utility on our Mac.
3 of 5 steps show a real screenshot from our MacBook Pro.
What changed: added which format to pick.
Steps
- 1
Copy off anything you need
Erasing removes every file on the drive, and it cannot be undone.
- 2
Open Disk Utility
Press Command + Space, type Disk Utility and press Return.
- 3
Show all devices and select the drive
Click the View button and choose Show All Devices. On our Mac the menu lists Hide Sidebar, Show Only Volumes (ticked) and Show All Devices. Then, in the sidebar, click the external drive at the top of its hierarchy, not a volume beneath it. No external drive is connected in our picture, so its sidebar shows only the Internal section.
- 4
Click Erase and choose a format
Click Erase in the toolbar. Our picture shows the internal Recovery volume group selected; make sure yours shows the external drive first. The Erase window that opens is not pictured. Apple's erase steps say to choose GUID Partition Map from its Scheme menu, then a format from the Format menu, such as APFS for a drive used only with Macs. For a Windows drive, Apple's Windows article says to choose a partition scheme, then MS-DOS (FAT) if the drive is 32 GB or less, or ExFAT if it is larger.
- 5
Name the drive and click Erase
Type a name. Apple says a drive for Windows can have a name of up to 11 characters. Click Erase, and Done when it has finished.
Which format to pick
- Only for Macs Choose APFS. Apple says it is the file system used by macOS 10.13 or later. Source: File system formats available in Disk Utility on Mac
- For a Mac and a Windows PC Choose ExFAT. Apple says MS-DOS (FAT) and ExFAT work with Windows, and to pick MS-DOS (FAT) for a drive of 32 GB or less and ExFAT for a larger one. Sources: File system formats available in Disk Utility on Mac, Format a disk for Windows computers in Disk Utility on Mac
If you do not see this option
- Only volumes are listed Our picture shows why: the View menu has Show Only Volumes ticked. Choose Show All Devices so the drive itself appears above its volumes.
- There is no Scheme menu Apple says this means a volume is selected. Select the storage device at the top of the hierarchy instead. Source: Erase and reformat a storage device in Disk Utility on Mac
- There is no Security Options button Apple says secure erase is offered only for some storage devices, and never for a solid-state drive (SSD). Source: Erase and reformat a storage device in Disk Utility on Mac
- You want to erase the Mac's own startup disk Apple says to start up in macOS Recovery and use Disk Utility there. To sell a Mac with Apple silicon or a T2 chip, Apple points to Erase Assistant instead. Source: Erase and reformat a storage device in Disk Utility on Mac
If this does not work
- The erase fails or the drive misbehaves Apple says to work from the inside out: run First Aid on each volume, then each container, then the device itself, with Show All Devices chosen.
- Disk Utility says the disk is about to fail Apple says to back up your data and replace the disk, because it cannot be repaired.
Good to know
Check twice that you selected the external drive and not the Mac's internal disk.
Always eject a drive before unplugging it: click the eject icon next to its name in Finder. This matters most with ExFAT, which is easier to corrupt.
That is also the reason behind the Windows drive puzzle: macOS can read drives formatted as NTFS, the usual Windows format, but cannot write to them.
For Time Machine backups, save yourself the job and let Time Machine format the drive itself: how to back up a Mac with Time Machine.
About this guide
- Device
- Mac
- Shown on
- macOS Tahoe 26 (MacBook Pro)
- App
- Disk Utility
- Path
- Disk Utility › View › Show All Devices
- Real screenshots
- 3 of 5 steps
- Checked
- October 2026
- Sources
- 4 official, linked below
Sources
Links checked October 2026. Menus and features can change with updates.What to do next
Free up and look after your Mac storage Step 3 of 4
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