Tutorial: How to repair disks in macOS with Disk Utility

If your Mac starts showing signs of trouble—it might not start up, applications might close unexpectedly, or certain files might not open—there's probably a problem with your hard drive. Luckily, Apple includes a very versatile and useful tool for these situations: Disk Utility . This built-in application lets you manage, repair, format , and verify internal or external drives on your Mac.

In this article, we'll tell you everything you need to know to use Disk Utility effectively. From how to access it, when to use it, how to run First Aid correctly, and what to do if nothing works. Beyond a simple guide, here you'll find detailed solutions, workarounds, tips, and best practices to ensure your disk is back in working order.

What is macOS Disk Utility and what does it do?

Disk Utility is a native macOS application designed to manage your Mac's storage system . It allows users to perform tasks such as partitioning and formatting disks, creating disk images, unmounting drives, and, most importantly in many cases, checking for and repairing errors using the First Aid feature . If you want to learn more about diagnosing and repairing hard drives and SSDs, you can consult our guide on using specialized disk diagnostic software.

This tool works for both internal drives (such as the boot disk) and external drives ( USB drives , hard drives, SD cards, etc.). It is especially useful when the system is behaving unusually, crashes when opening files, or the machine simply won't boot correctly.

When should you use Disk Utility?

There are several common signs that indicate your disk may have problems and that you should run First Aid from Disk Utility:

• The Mac takes a long time to start up or doesn't start at all.
• Disassembly or failure of external devices
• Apps that crash for no apparent reason
• Read errors when accessing certain files
• Corrupt files or inaccessible
• System messages warning of disk problems

How to access Disk Utility?

Depending on whether your Mac starts normally or not, there are different ways to open Disk Utility :

From a working Mac

1. Click on the Finder icon
2. Accede to Applications> Utilities
3. double click on Disk Utility

Using Spotlight

Press Cmd + Space and type “Disk Utility”. Press Enter to open.

If your Mac won't boot: from Recovery Mode

In this case you must access Disk Utility using recovery mode:

• On Macs with Apple Silicon chip: Shut down your Mac, press and hold The power button until the boot options appear. Click “Options” and then “Continue.”
• On Macs with a processor Intel: Reboot and hold the keys Cmd+R until the recovery screen appears.

What is “First Aid” and how does it work?

First Aid is a Disk Utility feature that analyzes and repairs logical errors in disk structures . It can correct problems with formatting, file systems, or directories without modifying your data. It's a safe operation: it doesn't delete or modify your files . For more information on how to repair disks and troubleshoot errors in Windows , you might find it helpful to review how to repair Windows startup.

When you run this function, it performs a full scan of the selected volume, container, or drive. If it finds errors, it will attempt to correct them immediately. You'll receive a message confirming whether the operation was successful or if any errors were found that it couldn't resolve.

Step by Step: How to Repair a Disk with Disk Utility

Before you begin, if you're going to repair the boot disk, it's critical to boot into recovery mode, as you can't repair a disk that's in use.

1. Open the Disk Utility from the corresponding environment according to your Mac type.
2. Click on View > Show all devices from the top menu.
3. In the left sidebar, you'll see all your disks, containers, and volumes. Always start from the lowest volume (usually Macintosh HD - Data).
4. Select the volume and press the button First Aid that you will see at the top.
5. Confirm with "Run" to begin the scan. Wait for it to finish.
6. Repeat the process going up the hierarchy: then the next volume, then the container, and finally the entire disk.

What if First Aid can't fix the disk?

When Disk Utility can't repair a volume , you'll see a message telling you so. This usually means the error is too serious. In this case, there are several possible solutions:

1. Repeat the repair

Run First Aid a second or third time. Sometimes it resolves minor errors on subsequent runs.

2. Check for “extension overlap” errors

This means that two files are sharing the same disk space. In this case, you'll need to check for conflicting files, which are usually stored in a folder called DamagedFiles . It may also be helpful to consult tools for repairing damaged disks in Windows.

3. Format the disk

If nothing else works, the most drastic but effective option is to completely erase the disk . This will delete all data, so you must make a backup beforehand . To do this:

1. Access Disk Utility
2. Select the problematic unit
3. Press on Delete and choose the file format you want (for example, APFS or Mac OS Extended)
4. Confirm and wait for it to finish

Once formatted, you can reinstall macOS from the same recovery environment and restore your data from a backup or Time Machine. To troubleshoot hard drive issues, you can also refer to .

Other ways to repair disks if Disk Utility fails

Apple offers other tools available for more complex situations. There are also advanced methods you can try if you're an advanced user:

Using the FSCK command

FSCK is a terminal- based diagnostic tool used to perform manual repairs in single-user mode. For more details, please see [link/reference].

1. Turn off your Mac and turn it on by pressing Cmd+S to enter single user mode
2. Write /sbin/fsck -fy and wait for the process to finish
3. If all goes well you will see the message “The Macintosh HD volume appears to be correct”
4. Write reboot to restart

Try third-party repair and recovery software

If neither FSCK nor Disk Utility can save your drive, applications like Disk Drill , EaseUS Data Recovery , or 4DDiG can recover data from damaged or formatted disks. Some are paid, but they offer limited free versions that allow you to check if your data is recoverable before purchasing.

Key tips to avoid data loss in the future

Prevention is better than cure. Here are several recommendations to take care of your discs and avoid major scares:

• Make frequent backups, preferably with Time Machine.
• Do not overload the disk: Try not to fill more than 80% of the available space.
• Do not disconnect external drives without properly ejecting them..
• Make sure you keep macOS up to date to get bug fixes.
• Avoid using unknown third-party tools to manage disks.

What does each button in Disk Utility mean?

At the top you will see several options, depending on the type of unit selected:

• First aid: analyzes errors and repairs them.
• Erase: formats the volume and deletes all data.
• Restore: clones another volume to the selected drive.
• Partition: divides the disk into independent sections.
• Mount/Dismount: makes a volume visible or invisible in the system.

What to do if your disk doesn't appear in Disk Utility?

If your disk does not appear, there may be a connection or hardware failure :

• Check cables and connections if it is an external disk.
• Check that it is powered correctly.
• Restart your Mac and access Disk Utility again.
• Starts in safe mode if you still don't see it.

If all else fails, it could be a physical problem with the disk. In that case, it's advisable to contact technical support or use specialized data recovery software.

macOS's Disk Utility is a powerful and versatile tool that, when used properly, can solve most storage-related problems without having to directly contact technical support. From verifying volumes, repairing logical errors, managing partitions, and performing secure formatting, mastering this utility is key to maintaining the performance and integrity of your computer. Additionally, if this tool can't resolve certain issues, there are always alternatives and specialized software to recover your data. Consistent backups and preventative maintenance help minimize risks and protect valuable information.

Related articles:

How to create, mount, and repair volumes with PowerShell in Windows

Isaac

Passionate writer about the world of bytes and technology in general. I love sharing my knowledge through writing, and that's what I'll do on this blog, show you all the most interesting things about gadgets, software, hardware, tech trends, and more. My goal is to help you navigate the digital world in a simple and entertaining way.