Methods to Format a Mac Storage Drive without Data Loss

Whether you are configuring an external storage drive on a Mac or formatting an internal disk drive, you need to ensure that the file system format is compatible.

Here are some file system formats that are required by different macOS versions –

• APFS format for macOS Ventura 13, Monterey 12, Big Sur 11, Catalina 10.15, or Mojave 10.14
• Mac OS Extended format for macOS Sierra 10.12 or earlier
• MS-DOS (FAT) or exFAT format to make your external storage drive cross-compatible with both macOS and Windows

Every new Mac system comes with a soldered flash memory chip formatted to a compatible file system. However, in the case of external drives, you may need to manually format the storage drive to the compatible file system.

Why Do We Need to Format Mac Hard Drive?

Irrespective of whether you are formatting the internal storage drive or the external drive, formatting helps in –

• Preparing the startup disk to reinstall macOS
• Resolving corruption or unreadable errors in the storage drive
• Changing the file system format of the disk drive for cross-compatibility
• Repair the disk drive in case the Disk Utility fails to repair it

However, storage drive formatting involves the risk of data loss. When you format the Mac storage drive to a new file system, macOS removes all references to the existing data that can lead to data loss.

In some cases, when you connect a corrupt or unreadable external storage drive to your Mac, macOS prompts you to initialize the disk. This can again result in critical data loss. Only use the initialize button on a new drive that is empty.

How to Format a Mac Storage Drive without Data Loss

Before formatting an external drive on a Mac, ensure that you have a backup of your data on iCloud or an external hard drive. Also, make sure that Time Machine backups are there. This way you can prevent data loss while formatting the Mac storage drive.

Method 1: Format the Startup Disk in macOS Recovery Mode

If you want to reinstall macOS or upgrade your macOS, you need to format your Macintosh HD startup disk. But you can’t format the startup disk while your macOS is running. So, you need to boot your Mac in macOS Recovery mode to access the startup disk and erase it using Disk Utility.

Once you’ve backed up your Macintosh HD data on an external hard drive or by using Time Machine, perform the following steps to format your startup disk and reinstall macOS –

• Restart your Mac and immediately press and hold Command + R key combination. Release the keys once you see the Apple logo or spinning globe.
• In the macOS Utilities window, click Disk Utility, and then click Continue. In the Disk Utility window, choose View > Show All Devices.
• From the left panel, select Macintosh HD and click the Erase tab. Provide the Name, Format, and Scheme in the respective field, then click Erase.
• Once Disk Utility formats the drive with a compatible file system, quit the app.
• Connect your Time Machine backup drive to your Mac. From macOS Utilities, select Restore from Time Machine Backup, and click Continue. Follow the onscreen instructions to reinstall macOS and restore data.

Alternatively, you can also select the Reinstall macOS option from macOS Utilities to install a fresh copy of macOS from the recovery drive or cloud.

Method 2: Format an External Hard Drive Using Terminal

To format an external hard drive, other storage drive, or non-boot volume on Mac, use Disk Utility directly from the Desktop and perform the erase operation. There are chances that the Disk Utility might throw an error while erasing an external storage drive. In that case, you can format the external drive on a Mac via the Terminal. Here are the steps to do this –

• Press Command + Space Bar to open Spotlight. Type ‘terminal’ and hit Return to launch the Terminal application on your macOS.
• In the Terminal window, type diskutil list. Note the name and identifier of the external storage drive. Ensure you have backed up all the data from the external drive.
• 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 is completed, the storage drive will have a new file system. Now, you can use the newly formatted drive to back up data.

Recover Data Lost due to Accidental Formatting

In case you have lost your data after formatting an external hard drive without taking a backup, you can leverage Stellar Data Recovery Professional for Mac. It is a specialized Mac data recovery software that helps you recover data from APFS, HFS+, FAT, ex-FAT, or NTFS file system formatted storage drives.

The software supports the latest macOS Sonoma and works on both Apple-Silicon Macs. This utility can save your day if you have formatted your Mac disk drive. Additionally, the software recovers emptied files from Trash such as Word, Excel, Photos, Videos, Audio, and more.

If you have lost your data due to accidental formatting an external drive on a Mac, you can use a professional Mac data recovery software to retrieve your lost data. Here are the steps –

• Download and install Stellar Data Recovery Professional for Mac on your Mac.
• On the Select What To Recover screen, let the default selection of Everything remain toggled on, and click Next.
• On the Select Location screen, select the formatted Mac hard drive, turn on Deep Scan, and click Scan.
• Once the scan is over, preview all the recoverable files. Click Recover, specify the save location, and click Save.

Note – The trial version of Stellar Data Recovery Professional for Mac software can scan the media and show a preview of recoverable files. To save the files, you need to activate the software.

Conclusion

To format your Mac startup disk or external storage drive safely, you must first back up the drive to avoid unwanted data loss. You can format your Mac hard drive via Disk Utility or by using Terminal commands. But be careful while executing the Terminal commands, as any wrong operation can result in permanent data loss.

And if you’ve accidentally formatted your Mac hard drive or SSD, without having any backup, use Stellar Data Recovery Professional for Mac, to recover lost data.

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About The Author

Vishal

Vishal is a data recovery expert @Stellar. He addresses data loss scenarios on a Mac. He intends to help people solve their macOS problems. Besides, Vishal prefers to read about astronomy and autobiography, and his favorite is Steve Jobs - The man who thought different written by Karen Bluementhal.