How to Format an External Hard Disk or USB Flash Drive on Mac OS

Quite often, when you purchase a new USB flash drive or an external hard disk, you may have to format it to ensure that it is compatible with your Mac device. This happens mostly because of the fact that they are all configured to be compatible with Windows device. While the disk may operate in a completely flawless manner, there may be some Windows components like MSDOS, FAT32, ExFAT, NTFS, and FAT formats that Mac cannot read. Therefore, formatting the external hard disk or USB flash drive can make it easier for the device to run on the Mac environment.

Here is a step-by-step guide on how to format an External Hard Disk or a USB Flash Drive on Mac

  1. Connect the hard drive to your Mac device.
  2. Head over to Applications, then Utilities to launch the Disk Utility.
  3. Identify your drive from the menu on the left hand side of the Disk Utility.
  4. Click on the name of your drive.
  5. In the top tab, select the Erase
  6. Click on field next to the Format From the drop-down menu, choose the Mac OS Extended (Journaled) option.
  7. If you wish to name the drive, you can do it now. However, if you opt out of naming the drive, you can also do it any time later.
  8. Click on the Erase button on the bottom-right corner.
  9. Confirm the action by clicking on Erase in the pop-up screen.
  10. Your system will begin formatting your external hard disk. The time taken depends on the size of the drive and the volume that has been occupied.

Remember, formatting a disk will result in loss of any data stored on the drive. You will also lose all disk partitioning. Therefore, create a backup of your data to ensure that you do not lose all your data. Following the process outlined above will make your external drive compatible with your devices running on Mac OS. Do keep in mind that this would be an unnecessary step if you wish to use your external hard disk or USB flash drive interchangeably between Windows and Mac devices. This procedure is exclusively for using these drives on Mac supported devices.

Also, if you intend to create a Mac OS installer drive or a bootable Mac OS drive, you will first have to format the disk drive by following the steps mentioned above.

Mia Watson is a self-professed security expert; he has been making the people aware of the security threats. His passion is to write about Cybersecurity, cryptography, malware, social engineering, internet and new media. He writes for Norton security products at

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