Disk Utility for Mac: Erase a volume using Disk Utility
You can erase and reformat an entire volume. If the volume contains data, it is deleted when you erase and reformat the volume, so make sure you create a backup of it if you want to keep the data.
WARNING: To erase your computer’s startup disk, you must start up from another disk. Before you erase your startup disk, make sure you create a backup of it.
You can erase disks or volumes. Erasing a disk deletes all its volumes and files. Erasing a volume deletes all the files on that volume, but does not affect other volumes.
Important: If you have any files you want to save, be sure to copy them to another disk before you erase the disk they are on.
Select the disk or volume in the sidebar, then click the Erase button .
Click the Format pop-up menu, then choose a volume format.
Mac OS Extended (Journaled): Uses the Mac format (Journaled HFS Plus) to protect the integrity of the hierarchical file system.
Mac OS Extended (Journaled, Encrypted): Uses the Mac format, requires a password, and encrypts the partition.
Mac OS Extended (Case-sensitive, Journaled): Uses the Mac format and is case sensitive to folder names. For example, folders named “Homework” and “HOMEWORK” are two different folders.
Mac OS Extended (Case-sensitive, Journaled, Encrypted): Uses the Mac format, is case sensitive to folder names, requires a password, and encrypts the partition.
MS-DOS (FAT): Use for Windows volumes that are 32 GB or less.
ExFAT: Use for Windows volumes that are over 32 GB.
Enter a name for the disk or volume.
To prevent the erased files from being recovered, click Security Options, use the slider to choose how many times to write over the erased data, then click OK.
Writing over the data three times meets the U.S. Department of Energy standard for securely erasing magnetic media. Writing over the data seven times meets the U.S. Department of Defense 5220-22-M standard.
Click Erase, then click Done.
Note: With a solid-state drive (SSD), secure erase options are not available in Disk Utility. For more security, consider turning on FileVault encryption when you start using your SSD drive.