Disk Utility for MacOS Sierra: Erase a Volume with Disk Utility

You can erase and reformat an entire volume. If the volume contains data, it will be deleted when erasing and reformatting the volume; so make sure you back up the data if you want to keep them.

WARNING: To erase the computer’s startup disk, you must boot it from another disk. Before erasing the boot disk, be sure to create a backup copy.

You can erase disks or volumes. When you erase a disk, all its volumes and files are deleted. Deleting a volume deletes all the files it contains, but not those stored in the other volumes.

Important: If there are files you want to save, copy them to another disc before erasing the disc in which they are located.

  1. Select the disk or volume in the sidebar and click the Delete button .
  2. Click the Format drop-down menu and select a volume format.
    • Mac OS Plus (with registration): uses the Mac format (HFS Plus with registration) to protect the integrity of the hierarchical file system.
    • Mac OS Plus (with registration, encrypted): uses the Mac format, requires password and encrypts the partition.
    • Mac OS Plus (upper / lower, with registration): uses the Mac format and distinguishes the case of folder names. For example, the “Tasks” and “TASKS” folders are different.
    • Mac OS Plus (registry key, encrypted): uses the Mac format, distinguishes the case of folder names, requires password, and encrypts the partition.
    • MS-DOS (FAT): Used for Windows volumes up to 32 GB.
    • ExFAT: Used for Windows volumes of more than 32 GB.
  3. Enter a name for the volume or disk.
  4. To prevent recovery of deleted files, click “Security Options”, use the slider to select how many times you want to overwrite deleted data, and then click OK.Overwriting data three times meets the US Department of Energy’s standard for safe erasure of magnetic media. Overwriting the data seven times meets the 5220-22-M standard of the United States Department of Defense.
  5. Click Delete, and then click OK.

Note: With a solid state drive (SSD), no safe erase options are available in Disk Utility. For more security, consider enabling FileVault encryption when booting with an SSD.


Create partitions on a physical disk
Format a disk for Windows computers
Encrypt and protect a disk with a password

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