How to Format an External Drive in OS X

Most external drives ship in formats that are universally recognised amongst nearly all operating systems (FAT, I’m looking at you), but there may be times where you might want to completely wipe a drive and/or set it up to be compatible with Apple’s Mac lineup only. Either way, you’ll want to format your drive accordingly.

Formatting an external drive on your Mac is quite easy, though it isn’t as evident and obvious as it is on a PC. You can format a drive in OS X using two applications: Disk Utility and Terminal

We’ll be detailing both of these methods below.

Formatting a disk using Apple’s Disk Utility is the easiest and most straight-forward method of the two. To format a disk using Apple’s Disk Utility, simply follow the steps below.

1. Open up Disk Utility on your Mac. You can either do this by searching for it from Spotlight or by navigating to “Applications -> Utilities” and opening Disk Utility.


2. Select the disk you want to format from the left-side pane.


3. You’ll see the option to “Erase” the disk at the center – top of the window.


4. Once you click on it, you’ll have the option to rename the disk, select the format you want for the disk (more on that later), and select the disk scheme.


5. Once you have everything selected, simply click on Erase, and you’ll have a newly formatted disk.

This method is aimed towards power users who are fond of using Terminal to do work on their Mac. It is a little longer but often comes in useful when Disk Utility refuses to perform your desired action for some reason.

To format an external disk using Terminal, simply follow the steps below:

1. Open Terminal, either by Spotlight or by opening the app from “Applications -> Utilities.”

2. Enter the following command into Terminal:

diskutil list

3. Once you enter in the command, you’ll get a list of your connected external hard disks to your Mac.


4. What you need to note down is the specific disk identifier for the external disk you’ll be formatting: this can be found in front of the specific disk. For example, the Identifier for the main external disk is “disk2.”


5. Once you have the disk identifier noted, you need to type in the following command into Terminal and replace each term as follows:

diskutil eraseDisk JHFS+ diskname diskidentifier

In the command above, change “JHFS+” to “HFS+” if you want a volume that is not journalled. Change “diskname” to the new name you want for the disk, and replace “diskidentifier” to the Disk Identifier obtained from Disk Utility. If you want to reformat, replace eraseDisk with reformat and delete the “JHFS+” and “diskname” parts of the command.


Use eraseDisk to erase the entire external disk, or eraseVolume if you just want to erase a particular partition. For example, I’d use “disk2s2” if I wanted to erase Untitled only in the example below:


Once done, press Enter, and your disk should be erased and formatted completely.

With Disk Utility, you have 3 main formats that you can erase your disk to.


MS-DOS (FAT) is the most popular format amongst external hard disks, as it’s both readable and writable by nearly all operating systems, Windows and OS X included. One of the major limitations of this format is that it’s not able to write files larger than 4GB, which can be quite a setback. But apart from that, this will be the format you’ll want to use if you want a drive with cross-compatibility for quick transfers, or temporary storage. Most drives are formatted in MS – DOS (FAT) out of the box.


ExFAT is for those of you who are finding it hard to use FAT with all the limits, especially the large file transfer issue. ExFAT is basically an extension of FAT that allows for larger file sizes to be written and more. Note that ExFAT is only compatible with versions of Windows later than Vista.

OS X Extended

OS X Extended is Mac’s native drive format. Your internal Macintosh drive is also formatted in this format. It’s recommended to use this format whenever you need to use an external drive with OS X only.

One interesting feature of OS X Extended is that it is case-sensitive, i.e if you specifically name a file “BeachShot1,” OS X will see that file as different from a similar file named “beachshot1.”

While formatting your disk to OS X Extended, you’ll have four main options:

  • OS X Extended (Journaled)
  • OS X Extended (Case Sensitive, Journaled)
  • OS X Extended (Journaled, Encrypted)
  • OS X Extended (Case Sensitive, Journaled, Encrypted)

Journaled is basically an extension feature to the format that ensures files are fully written to the drive in a location called the Journal before they are committed as stored data, which helps guarantee file integrity if there is an interruption such as a power loss, drive failure, etc.

Encrypted, as the name suggests, will make sure your drive and its contents are encrypted.

Let us know in the comments section below if you have any question or query.