Whether you need to better organize your hard drive or resolve disk errors, Disk Utility is the tool for the job. Built into macOS, Disk Utility is tucked away in the Utilities folder, which is inside the Applications folder, but it’s easy to locate using Spotlight, which is activated by pressing Command+Spacebar and then simply typing Disk Utility.
The tool displays details and a graph of your hard drive configuration, showing the overall capacity as well as used and free space and the various volumes.
Over the years, Disk Utility has been revised several times, so the options may be slightly different depending on the version of macOS you’re using. For example, in Mac OS X El Capitan Disk Utility was redesigned and many of the features were evolved or removed. There were also some changes in macOS High Sierra thanks to the new file format that Apple introduced: APFS. And when Catalina arrived, a new Macintosh HD: Data volume started showing up alongside a read-only Macintosh HD system volume.
Why use Disk Utility
You can use Disk Utility to do the following:
Erase, format or manage internal drives and external storage devices.[ Read: How To Format A Drive On A Mac ]
Diagnose and fix problems with a damaged disk or volumes. (See: How to check your Mac’s disk status using Disk Utility.)
To erase, format or partition a disk or volume. (See: How to partition a Mac drive or create an APFS volume.)
To encrypt storage devices or add a password to protect a drive.
To mount, unmount, or eject a disk.
To change the file system, for example, to enable or disable journaling.
Work with RAID sets. Combining multiple drives into a RAID set that acts as a single drive can increase performance, reliability, and storage space.
Create a disk image of the files you want to move to a different computer, archive, or back up.
Disk Utility used to be used to check and repair permissions, but since El Capitan this is not necessary.
You may want to use Disk Utility if you experience the following:
Here’s how to perform the most common Disk Utility tasks.
How to tell if your disk is bad using Disk Utility
If you think there’s a problem with the drive inside your Mac or an external storage device, you can use the First Aid feature in Disk Utility to check.
The First Aid feature in Disk Utility will run several checks and if it detects a problem with your disk, it will repair it.
Note that you cannot use First Aid to repair your startup drive while the operating system is running. We will see how to do it below.
Here’s how to run First Aid on your Mac or an external drive to check for a problem with the drive:
Open Disk Utility.
Select the device you’re having issues with in the sidebar. Click Show All Devices (in the dropdown menu above View) if you don’t see it.
Click First Aid.
Disk Utility will check the volume for errors and repair it if necessary. Click Run.
While Disk Utility checks the volume, you won’t be able to use your Mac; note that it could take a long time.
If it finds a problem with the disk, Disk Utility will try to repair it.
If Disk Utility can’t repair the drive or thinks the drive is about to fail, it will warn you. If this is the case, you should back up your data before it’s too late. Read this article on how to back up your Mac. You may also find this useful: How to recover and delete data from a failed hard drive, SSD, or external drive.
If Disk Utility reports that the disk is OK, then there is nothing wrong with the disk.
How to repair your boot disk/startup disk with Disk Utility
You can run First Aid on your startup drive by following the steps above, but if Disk Utility encounters any errors, it won’t try to fix them.
If you need to repair your Mac’s startup drive (the boot volume), you won’t be able to do it, since Disk Utility can’t repair the mounted volume (from which everything runs).
In this case, you need to start your Mac in recovery mode and repair the disk from there. This way things can be run from the Recovery HD volume that was created when macOS was installed.
The method to access Recovery depends on your Mac:
If you have an M1-series Mac, shut down your Mac, then press and hold the power button while it starts up.
If you have an Intel Mac, restart your Mac and hold down Command-R on your keyboard.
We have a detailed tutorial on using recovery mode here.
To repair your startup disk:
Boot into Recovery by following the steps above.
Once your Mac has booted into Recovery, you’ll see a Utilities screen. Choose Disk Utility.
Select the drive you want to repair from the menu and click First Aid.
As stated above, Disk Utility will run its checks and try to repair if it can.
The repair process may take a while.
For more information, read How to Check Your Mac’s Disk Status Using Disk Utility.
How to format a disk using Disk Utility
There are a number of reasons why you might want to format a drive. Maybe you want to wipe your startup drive so you can perform a fresh install of OS X, maybe you want to encrypt an external storage drive you use for work, or maybe you want to create a partition for Windows or a different version of the Mac operating system. .
There are several file formats that you may want to use, including:
Apple File System (APFS): The Apple File System since macOS 10.13.
Mac OS Extended – Apple’s file system prior to macOS 10.13.
and MS-DOS (FAT) and ExFAT, for compatibility with Windows.
We have a step-by-step guide to format a drive on Mac here.
When you format a drive, you can also add encryption and other security features.
How to use Disk Utility when a drive won’t mount
If you connect a hard drive or flash drive to your Mac and you don’t see it and it won’t let you access your data, read: What to do if a hard drive won’t mount.
How to create a disk image using Disk Utility
Disk Utility can create a disk image of the contents of a folder that you can then transfer to another Mac, a file, or any location that doesn’t accept folders.
It’s similar to compressing the folder into a zip file, but the benefit is that you can not only use disk image compression to save space, but you can also take advantage of Apple’s encryption for the disk image.
Follow these steps to create a disk image using Disk Utility.
How to partition a disk or create a volume
You may want to partition a drive to divide it into separate containers or because you want to install multiple operating systems. How you do this will depend on the version of macOS you’re running. On newer Macs, instead of creating a partition, you need to create a volume.