How to Format Your Mac Hard Drive without Data Loss?

Format Mac hard drive without data loss

This blog post shares a few easy methods to format a Mac storage drive in the desired file system, without the risk of data loss. Read on to know how you can erase a Mac storage drive easily with the help of Disk Utility and Terminal. Also, learn about the risks and how to overcome them effectively.

As you are aware, an internal or external Mac storage drive requires formatting to work properly. You have different choices of file systems, namely APFS for macOS 10.14 or 10.13, Mac OS Extended for macOS 10.12 or lower, and MS-DOS (FAT) or ex-FAT for Windows compatibility.

A new Mac with its inbuilt SSD comes pre-formatted with a file system that contains the macOS itself. You may need to format a Mac drive or volume in the following situations:

  • Resolve corruption or unreadable error of the storage drive
  • Format the startup disk to reinstall macOS
  • Change file system format of an external drive (e.g. HFS to APFS or APFS to ex-FAT)
  • Format the storage drive in case Disk Utility fails to repair it

[Important Note]:

  1. As formatting a drive removes all references to the data stored on it, it’s important to back up the drive before you erase/format it.
  2. When you connect a corrupt/unreadable drive to your Mac, macOS will prompt you to initialize the disk. DO NOT click the Initialize button…read more in the bonus tips section at the end of this post.

Steps to Format a Start-up Disk Drive on Mac

Backup your Mac

Before formatting, back up the Mac start-up drive to an external storage medium to ensure that no data is lost in case of unexpected events. You can use the Time Machine backup.

Read More How to Set Up Time Machine on Mac

Open Disk Utility in macOS Recovery Mode

To format a startup disk on Mac, you need to open Disk Utility in macOS Recovery mode, as follows:

a) Restart your Mac and immediately press and hold Command + R keys.

reboot macOS with Command + R

b) Release the keys once you see the Apple logo or spinning globe.

c) In the macOS Utilities window, click Disk Utility and then click Continue.

macOS utilities

Note: To format Mac external storage drive, you can open Disk Utility directly from Desktop.

d) Press Command + Space Bar to open Spotlight, then type ‘disk utility’ and hit Enter.

Format by Using Disk Utility

a) In the Disk Utility window, choose View > Show All Devices.

b) From the left panel, select the storage drive or a volume to format.

c) Click the Erase tab. Provide the Name, Format, and Scheme in the respective field then click Erase.

d) Your drive will be formatted with the opted file system.

How to Format External Hard Drive on Mac with Disk Utility

How to Format External Storage Drive on Mac without Disk Utility?

You can use the above steps to format an external storage drive as well. But, sometimes Disk Utility throws an error while erasing an external storage drive. In that case, you can format the external drive on Mac by using Terminal, as described below:

1) Press Command + Space Bar to open Spotlight. Type ‘terminal’ and hit Enter.

2) In the Terminal window, type diskutil list (Note the name and identifier of the external storage drive)

3) Type diskutil eraseDisk FS DN D# (Here replace the FS with the required file system format, DN with the name of the drive, and D# with the drive’s identifier)

When the process completes, the storage drive is erased to the correct file system format.

How to recover data from an accidentally formatted Mac hard drive?

Wait! Did you accidentally format a wrong hard drive on your macOS?

Or, erased the Mac external drive without backing it up in the first place?

Data loss can happen to any of us. Further, Disk Utility does not provide any option to undo format. But you can get back your formatted data from the Mac hard drive by using a Mac hard drive recovery software, as explained next.  

Download, install & launch the Trial* version of Stellar Data Recovery Professional for Mac.

Launch Mac data recovery

On the Select What To Recover screen, let the default selection of Everything remain toggled on, and click Next.

Recover data from formatted Mac

On the Select Location screen, select the formatted Mac hard drive, turn on Deep Scan, and click Scan.

Mac formatted disk recovery

Once the scan is over, preview all the recoverable files.

Mac formatted external drive recovery

To save the recovered files, activate the software. Read More: How to Activate Stellar Data Recovery Professional on your Mac?

Click Recover, specify the save location, and click Save.

Undo Mac erase disk utility

*The trial software can scan the media and show preview of recoverable files. To save the recoverable files, you need to activate the software.

The software saves the recovered data from the formatted storage drive to any location of your choice. You can visit the save location to verify your recovered data.

Bonus Tip: Safely Fix Storage Drive Unreadable Error

When you connect a corrupt or unreadable drive to your Mac, macOS will prompt you to initialize the disk. DO NOT click the Initialize button if the disk contains vital data, instead click Ignore to overlook the error or click Eject to eject the storage drive. Recover the inaccessible data from the storage drive by using a Mac hard drive recovery software prior to initializing it to the right file system.

Mac hard drive initialize

For a new drive with no file system or the unreadable drive whose data is recovered, click the Initialize button on the error message box. In the Disk Utility window, perform the erase operation to initialize the disk with automatically chosen file system format.


The blog post shared simple methods to format Mac start-up drive and external drive with a compatible file system without losing data. The best way is to back up the drive and use Disk Utility to format it.

In case Disk Utility fails to format the drive, advanced users can use Terminal to perform the same task. However, be cautious while using the Terminal commands.

The blog also suggested initiating Mac hard drive recovery if the drive was formatted accidentally and didn’t have the backup. Stellar Data Recovery Professional is specialized software that can help you salvage the data from accidentally formatted Mac hard drives.

The software supports a variety of hard drive brands, USB 2.0 and 3.0 alongside firewire and Fusion Drives.

Remember: The best data recovery result is achieved when the formatted storage drive is not overwritten. So, it’s important to stop using the drive immediately to avoid overwriting, and use Mac data recovery software to get back the data from accidentally formatted hard drive.

  1. Dorothy September 24, 2019
    • Vishal September 25, 2019
  2. Frances Schaff August 23, 2019
    • Vishal August 27, 2019
  3. Refugio I. Brand June 25, 2019
    • Vishal June 26, 2019

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