Format (erase) external hard drives on a Mac

On a Mac it is of course also possible to format an external hard drive. You can then completely erase and restore the drive so you can use it again with no files left behind. You don’t need any extra application for this as you can do this with ‘Disk Utility’.

When using an external drive on a Mac, remember that it must be compatible with macOS. For example, not all Windows-formatted drives can be used on a Mac. The structure of the disk depends on your own wishes, for example you can choose to format a disk so that it works on both Windows and Mac.

Format external hard drive on Mac

• Connect the hard drive to your Mac
• Open ‘Disk Utility’ from Finder ▸ Apps/Programs ▸ Utilities
• Select the disk in the left column
• Click ‘Delete’ in the toolbar

Enter a desired name and click on the drop-down menu under ‘Structure’. Choose a desired option, below we explain the different options. If necessary, click on ‘Security option’ to overwrite the disk several times during the erase. Then click ‘Erase’ to format the disk. Depending on disk space, it takes a few seconds for the USB Stick/Drive to be formatted. From that moment on you can use the external hard drive or USB as usual.

Different structures while erasing hard drive

When you are going to erase and restore a hard disk or USB stick, you have different formats to choose from. If you are only going to use the hard disk on a Mac, you can choose the Mac OS formats. If you also want to use the hard disk on Windows, you must choose a different structure, you will find additional explanation below.

Mac OS Extended (Journaled)

This is the default format for Mac disks (HFS+). The hard disk of a Mac is also formatted according to this structure. Can only be used on a Mac, you must choose this format if you want to use the disk for Time Machine.

Mac OS Extended (journaled, encrypted)

Same function as described above, but you must enter a password for this drive to protect it. Files, etc. are also stored encrypted.

Mac OS Extended (case sensitive, journaled)

Mac-specific structure, but folders and files are case-sensitive. This means that, for example, the folders ‘appletips’ and ‘APPLETIPS’ are considered two different folders. It is therefore best to choose this structure if you know what you are doing.

Mac OS Extended (case sensitive, journaled, encrypted)

Same function as described above, but you must enter a password for this drive to protect it. Files, etc. are also stored encrypted.

ExFAT

Can be used by both Mac and Windows. Please note that this version only works from Windows 7 (without restrictions) and OS X 10.6.5 (Snow Leopard). The structure has the ability to store files above up to 2 TB in size.

MS DOS (FAT):

Usable by both Mac and Windows, however, files on this drive cannot be larger than 4 GB. The advantage is that this structure works on all Windows and Mac operating systems. From macOS High Sierra, files on this drive cannot be larger than 2 GB, exFAT is a better alternative in this case.

What about the APFS format?

Since macOS High Sierra it is also possible to format an external hard drive with the new APFS (Apple File System). The volume you want to use for this must meet the condition that the partition layout is set to ‘GUID partition layout’. It is not necessary to format your external hard drives to APFS, because macOS also works fine with the old variants.

However, APFS has some advantages, such as better encryption, less storage space is used and the chance of damaged (corrupt) files is smaller. You can read all the information about formatting external hard drives to APFS here.