How to erase a disk for Mac

Use Disk Utility to erase (format) a hard disk, SSD, flash drive, or other storage device.

Erasing a disk or volume permanently deletes all of its files. Before continuing, make sure that you have a backup of any files that you want to keep.

How to erase a disk

Proceed based on whether you're erasing your startup disk or some other disk. Your startup disk is the disk (volume) that your Mac started up from. By default it's the disk built into your Mac, named Macintosh HD. If you're selling, giving away, or trading in your Mac, you should erase your startup disk.

Erase a startup disk

  1. Start up from macOS Recovery.
  2. Select Disk Utility from the Utilities window in macOS Recovery. Then click Continue. The macOS Utilities window in Recovery
  3. Make sure that the sidebar in Disk Utility shows the name of your startup disk. The volume representing your startup disk is Macintosh HD, unless you renamed it. 
  4. Look for a ”Data” volume with the same name, such as ”Macintosh HD - Data.” If you have such a volume, select it. Then choose Edit > Delete APFS Volume from the menu bar, or click the delete volume button (–) in the Disk Utility toolbar. When you're asked to confirm, click the Delete button. Do not click Delete Volume Group. Do the same to delete other volumes you might have on your startup disk—except the volume named Macintosh HD.
  5. After deleting any Data volumes, select Macintosh HD in the sidebar.
  6. Click the Erase button or tab, then complete these items:
    • Name: Enter a name that you want the volume to have after you erase it, such as Macintosh HD.
    • Format: Choose either APFS or Mac OS Extended (Journaled) to format as a Mac volume. Disk Utility shows the recommended Mac format by default.
  7. Click Erase to begin erasing. You might be prompted to enter your Apple ID. Erasing Macintosh HD in Disk Utility
  8. When done, quit Disk Utility to return to the Utilities window. 
  9. If you want your Mac to be able to start up from this volume again, choose Reinstall macOS from the Utilities window, then follow the onscreen instructions to reinstall macOS on the volume. If you don't reinstall macOS, your Mac might start up to a flashing question mark (?).

    Erase some other disk

    The steps above also work when erasing a storage device that you're not using as a startup disk. However, in that case it's not necessary to open Disk Utility from macOS Recovery: you can instead open it from the Utilities folder of your Applications folder. And you don't need to delete data volumes first: just select your disk in Disk Utility, then click Erase.