How to Fix "The Disk Macintosh HD Can't Be Unlocked" Error

There are various reasons why you might need to change the macOS version on your Mac, whether it’s reinstalling, upgrading, or downgrading. Ideally, this process should be smooth if done correctly. However, unexpected errors can occur, which can be quite frustrating.

In this article, we will explore the error message "The disk Macintosh HD can’t be unlocked" and, in some cases, "The disk Macintosh HD - Data can’t be unlocked." We will explain what these errors mean, why they happen, and how you can fix them.

What Is 'The Disk Can't Be Unlocked' Problem?

If you have FileVault enabled on your Mac, or if your Mac has a T2 security chip or M-series chip, Macintosh HD is encrypted and must be unlocked when changing the macOS version during reinstallation, downgrade, or upgrade. However, this unlocking process can sometimes fail.

If the failure occurs on a Mac running macOS Mojave or earlier, you will see the error message "The disk [Your Mac Disk's Name] can't be unlocked."

Starting with macOS Catalina, Mac’s internal hard drive is automatically split into two volumes to store data: Macintosh HD and Macintosh HD - Data. One is the system volume that contains the macOS, and the other is the data volume that stores user data. If the unlocking error affects the system volume, it displays as "The disk Macintosh HD can't be unlocked." If it affects the user data volume, you will see "The disk Macintosh HD - Data can't be unlocked."

Why Can't Macintosh HD Be Unlocked?

These error messages indicate that a problem was detected with the disk that prevents it from being unlocked, but they don’t clearly state the exact cause. From our experience and user feedback, the "The disk Macintosh HD can't be unlocked" error is commonly triggered by FileVault encryption, disk errors, or a duplicate Macintosh HD - Data volume. We will go over the solutions shortly.

Disk errors on your Mac can occur when your system is underperforming due to accumulated cache, conflicting apps, or low memory. Regular maintenance, such as clearing junk files, freeing up RAM, and creating more storage space, can help prevent these errors. To streamline these tasks, consider installing BuhoCleaner on your Mac for a complete system clean-up. This may also help in solving the disk issues that make your Macintosh HD unable to unlock.

1. Download and open BuhoCleaner on your Mac.
2. From the sidebar, select a task and follow the onscreen instructions.
   • Flash Clean
   • App Uninstall
   • Large Files
   • Duplicates
   • Startup Items
   • Toolkits - Free Up RAM

     

3. Try to unlock your Macintosh HD again.

How to Fix The Disk Macintosh HD Can't Be Unlocked Error

The disk unable to be locked message doesn't provide an option to enter a password to unlock Macintosh HD and only shows an unhelpful OK button. But don't worry—learn how to unlock Macintosh HD using the following methods.

Before attempting to fix the "Macintosh HD can't be unlocked" issue, take a moment to back up your Mac. Since you're working with your internal disk and personal data, it's crucial to secure your files first. Here is how to back up your Mac with Time Machine:

1. Connect an external hard drive to your Mac.
2. Open the Apple Menu > System Preferences > Time Machine on macOS Monterey or earlier; Open the Apple Menu > System Settings > General > Time Machine on macOS Ventura, Sonoma and Sequoia.
3. Select your connected hard drive as the backup drive and click Set Up Disk.
4. Complete setting up your backup disk.

The initial Time Machine backup may take some time, depending on the size of your files. Once your system is backed up, you can proceed with fixing the unlockable Macintosh HD issue.

Turn FileVault Off

If FileVault is enabled on your Mac, it might have glitches that can cause issues with unlocking the disk. Before making any system changes, be sure to disable FileVault on Mac. Decryption can take hours if you have a large amount of data, but you can continue using your Mac as usual during this process.

• On macOS Ventura or later:

  1. Click on the Apple menu > System Settings > Privacy & Security.
  2. Scroll down to select FileVault.
  3. Click the Turn Off button.
  4. Click Turn Off Encryption.

• On macOS Monterey or earlier:*

  1. Click on the Apple menu > System Preferences > Privacy & Security.
  2. Go to the FileVault tab in the Security & Privacy window.
  3. Click on the lock at the bottom left and enter your admin username and password.
  4. Click Turn Off FileVault.
  5. Click Turn Off Encryption.

Run First Aid in Recovery Mode

A damaged or corrupted file system can cause a disk-locked situation. The simplest way to check and repair Macintosh HD is by using the First Aid feature in Disk Utility while booting your Mac in Recovery mode. Intel-based and Apple Silicon Macs use different methods to enter macOS Recovery. Follow these steps:

• For Intel-based Macs: Restart your Mac from the Apple menu, then press and hold the Command-R keys until the Apple logo or spinning globe appears.
• For Apple Silicon Macs (M1 and later): Restart your Mac from the Apple menu, then press and hold the Power/Touch ID button until you see "Loading Startup Options." Select "Options" and then click "Continue."

How to run First Aid to repair Mac disk issues:

1. Select Disk Utility from the Utilities window and press Continue.
2. From the top menu bar, click View > Show All Devices Your internal hard drive should be listed in the following hierarchy:

• Mac internal hard drive
• Container
• Macintosh HD
• Macintosh HD - Data
• Other volumes

3. Select the last volume listed.
4. Click First Aid at the top, then click Run.

   

5. Repeat this process for the other volumes, the container, and the hard drive, working from the bottom up.
6. When the First Aid process is complete, click Done.

Delete Extra Macintosh HD - Data Volume

If running First Aid doesn't resolve the issue, try deleting any duplicate volumes you encountered during the process. This is often an extra "Macintosh HD - Data" volume or a "Macintosh HD - Data - Data" volume. Follow this guide:

1. Reboot your Mac into Recovery Mode using the instructions above.
2. Select Disk Utility from the Utilities window and press Continue.
3. Show all devices and locate the duplicate Macintosh HD - Data volume you want to delete.

   

4. Select the redundant volume and choose Erase.
5. Enter your admin password if prompted.

Erase and Reinstall macOS

The last resort to fix the "Macintosh HD can't be unlocked" issue is to perform a clean installation of macOS. This process involves erasing your Macintosh HD disk and reinstalling macOS on your Mac, which will eliminate any problems preventing the disk from being unmounted and unlocked.

Ensure that you have backed up your important data before proceeding, as these steps will permanently delete all your personal files.

1. Restart your Mac into macOS Recovery mode using the instructions above.
2. Open Disk Utility and click the View button to show all devices.
3. If you previously used Disk Utility to add volumes to your startup disk, delete all additional internal volumes using the delete volume (–) button in the toolbar.
4. Now select the Macintosh HD volume in the sidebar.
5. Click the Erase button, then specify the name as Macintosh HD and the format as APFS.
6. Click Erase. However, if you see an Erase Volume Group button, click that button instead.

   

7. If asked, enter your Apple ID.
8. When done, quit Disk Utility to return to the utilities window.
9. Select Reinstall macOS, then click Continue and follow the onscreen instructions.

Conclusion

This article addresses the error message "This disk Macintosh HD can't be unlocked. A problem was detected with the disk that prevents it from being unlocked." You will find four ways to resolve this issue. Before you start, run BuhoCleaner to optimize your Mac's performance and potentially solve disk errors, and remember to back up your Mac with Time Machine.