How to reformat an external drive for Mac

How to reformat an external drive for Mac

External hard drive not recognized on your Mac? Could be to file format

If you just bought a shiny new external drive that doesn’t work on your Mac, it might be incompatible with macOS. But unlike other electronics on the market, it is possible to reform an external drive to work with the operating system of your choice. It’s easy to do on a Mac using Apple’s built-in Disk Utility, and this is where we show you how.

Which file format should I choose?

When reformatting an external hard drive, the biggest decision you have to make is regarding the file format. You see, there is not one but several different file formats for you to choose, offering different levels of compatibility between different operating systems. The file format you choose depends very much on what you will do with the external drive, and what operating system you use every day.


APFS is the Apple file format choice for Mac running macOS High Sierra or newer. Introduced as a replacement for Mac OS Extended, this new file format offers increased efficiency and reliability, albeit cost: APFS is not compatible with pre-high Mac Sierra, and will not work with Windows or Linux machines. .

With a focus on speed and reliability, it shouldn’t be surprising that APFS is exclusive to SSDs and flash storage devices – if I have a standard external hard drive, you have to choose another option.

Mac OS Extended

If you are running macOS Sierra or a previous version of macOS / Mac OS X, Mac OS Extended is the default file format. This will play well with your Mac, but like APFS above, Mac OS Extended is not compatible with Windows or Linux PCs.

You can also choose Mac OS Extended (Encryption) to protect the data password on the drive – a great security feature for those who deal with sensitive data and / or travel with an external drive.


FAT32 is the first choice for many people, offering cross platform compatibility between Mac, PC and Linux, ideal for those who use multiple platforms every day. However, an aging file system has a major disadvantage: it is limited to a maximum of 4GB, and is also vulnerable to disk errors.


ExFAT is an improved version of FAT32. Like its older siblings, ExFAT is compatible with Mac, PC and Linux, but doesn’t have the same 4GB file limit. Although not as efficient as Apple’s APFS, universal support makes this make sense for most external hard drive users.


NTFS is the default file format for Windows PCs, and similar to Apple APFS and Mac OS Extended, it is only compatible with Windows machines. That being said, there is no way to reformat NTFS on a Mac (and why do you want to?) Without splashing third-party software.

To make it clearer, we recommend that you stay away from NTFS if you want to use an external hard drive on a Mac.

How to reform an external drive on Mac

Fortunately, reformatting an external drive on a Mac is a relatively easy process – Apple even sent a Mac with a built-in utility to do it. Note that reformatting the drive will erase everything stored on the drive, so make sure you transfer important files before you follow the steps below.

  1. Connect your external drive to your Mac.
  2. Open Disk Utility. You can search for applications by accessing Spotlight (Command + Space) or by going to Finder> Applications> Utilities.
  3. Select the external drive under the External Drive subtitle on the left. If you use more than one drive, make sure the drive you want to reform because the process is largely irrecoverable.


4. When you are ready, press the Delete button.

5. Enter the drive name and select the format of your choice in the Format dropdown menu.


6. Click Delete to reformat your drive – this should not take more than a few minutes, but this can vary depending on the storage size and type of drive you are using. You will also be asked if you want to run First Aid on the drive before deleting – this is more for those who have a damaged drive, so please skip if you want.

You are now ready to use an external drive on your Mac (along with Windows and Linux if you use ExFAT!). For more information on how to get the most out of your Mac and accessories, see how to use iPad as a second screen on a Mac, and how to use a PS4 or Xbox One controller on a Mac as well.

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