What is Macintosh HD, and why can’t it be unlocked?

If you're puzzled by “the disk Macintosh HD can't be unlocked” error, look no further. 

Many users report that an unexpected error message appears on their Desktop after upgrading their macOS or, in some cases, downgrading.

In this article, we'll look at what it means and, more importantly, how to fix it.

Before we get into the main troubleshooting tips, it's essential to understand what Macintosh HD data is, so jump to the next section for a quick walk-through.

What is Macintosh HD and Macintosh HD data?

Since macOS 10.15 Catalina, a MacBook's internal hard drive is segregated into two distinct entities: by default, one is called Macintosh HD, a read-only system volume that stores the operating system and the files macOS needs to run. Users cannot edit, erase, or alter this volume.

Macintosh HD — Data is the other separate volume, storing Mac user files like videos, documents, audio, and photos. Users have read-write access, meaning you can manage and edit files housed here.

So when you encounter “the disk Macintosh HD can't be unlocked” error, it simply means that the volume is locked and cannot be managed. On screen, the message is often followed by a second line: “A problem was detected with the disk that prevents it from being unlocked.”

In some cases, extra, duplicate locked volumes suddenly appear that may look like this: Macintosh HD – Data – Data. These are totally unnecessary and can be deleted — we'll get to that a little later in the article.

Why does “the disk can’t be unlocked” error happen?

Although it's not entirely clear why this error happens, there seems to be a correlation between upgrading or downgrading your macOS. Thankfully, we've got the tips you need to solve it.

Although scary-sounding, disk errors and other types of disk failures are pretty common, these issues can often be prevented or, in some cases, resolved by performing tasks like reindexing your Spotlight and repairing disk permissions.

The most straightforward way to perform these types of tasks is to use the Performance feature in CleanMyMac. It can handle these tasks in a few simple clicks and also free up purgeable space and thin out your Time Machine snapshots. 

You can test it for 7 days — get your free trial here,

Now, follow the steps below to get started:

1. Open the CleanMyMac app.
2. From the sidebar, select Performance and click Scan.
3. Press View All Tasks and select the following: Free Up Purgeable Space and Repair Disk Permissions.
4. Click Run.

Now let's get started with unlocking the disk on your Mac. 

Did you know? Another nasty Mac glitch is an application not opening (error message 10673). Here's an article on how to fix it.

How to solve "The disk Macintosh HD can't be unlocked" error

Before diving into the fixes, take a moment to back up your Mac — just in case. Here's how:

1. Connect your external storage drive.
2. From the main Apple menu, open System Settings > General > Time Machine (on older macOS versions: System Preferences > Time Machine).
3. Click Add Backup Disk, select your external drive, and click Set Up Disk (on older versions: Select Backup Disk > Use Disk).

Now that's covered, let's jump into the fixes.

Run First Aid

The easiest way to resolve the Macintosh HD data error is to run the First Aid feature from within Disk Utility while your Mac is booted in Recovery mode. 

The First Aid feature can inspect and repair your hard drive, container, and various volumes. Let's start with booting your Mac in recovery mode:

• For Intel-based Macs, shut down your Mac from the main Apple menu, then turn it back on and immediately press and hold Command-R until you see an Apple logo or a spinning globe.
• For Macs with Apple silicon, shut down your Mac from the main Apple menu, then press and hold the power button until you see "Loading startup options." Select Options, then Continue.

Now that you've booted your Mac in Recovery mode, here's how to run First Aid:

1. Select Disk Utility from the Utilities window.
2. From your top menu bar, press View > Show All Devices.
3. Locate your internal drive in the list and start with its volumes: select Macintosh HD — Data, click First Aid, and press Run.
4. Repeat this step for the following, in this order:

• Macintosh HD volume
• Any other remaining volumes
• The container
• The disk itself

This will help to fix and repair any disk errors. Once complete, boot your Mac up, as usual, to see if this issue is resolved.

Tip: Sometimes, updating your Mac to the latest macOS version can help fix this error message. If, for some reason, you cannot update your Mac, here's a guide on how to troubleshoot it.

Delete extra duplicate volumes

If running First Aid didn't seem to solve the issue, try deleting any duplicate volumes that you came across when running First Aid. 

To do this, reboot your Mac into Recovery Mode, using the steps from above, then follow the instructions below:

1. Once again, select Disk Utility from the Utilities window.

2. Locate the duplicate volume you want to erase from the list and select it. Make sure it is one of the redundant duplicates: do not erase the Macintosh HD or Macintosh HD — Data volume itself, because erasing the Data volume deletes your files.

3. Click Erase.

4. Enter your admin password if prompted.

Tip: To confirm which volume is the exact duplicate and can be deleted, check the Mount Point. Open Disk Utility and select one of the Data volumes. Look at the detailed text pane at the bottom center of the window. Now, find the line labeled Mount Point. You should keep the volume if its mount point is /System/Volumes/Data and can delete one with the mount point saying /Volumes/Macintosh HD - Data (or has a – Data 1 or – Data – Data path).

Erase and reinstall macOS

As a final step, it's also possible to erase and reinstall macOS to completely resolve the problem.

But as a word of warning, make sure you've backed up your data using Time Machine before following these steps. Erasing your macOS will remove all of your personal data. 

If your Mac has Apple silicon or the Apple T2 Security Chip and runs macOS Monterey or later, the quickest way to do this is Erase Assistant: from the Apple menu, choose System Settings > General > Transfer or Reset > Erase All Content and Settings (on macOS Monterey: System Preferences > Erase All Content and Settings in the menu bar), then follow the prompts.

Otherwise, use Disk Utility:

1. Boot up your Mac into recovery mode using the steps from above.

2. From the Utilities window, select Disk Utility and click Continue.

3. Select Macintosh HD in the sidebar, then press the Erase button and enter the following
   Format: APFS or Mac OS Extended (Journaled)
   Name: Macintosh HD

4. Select Erase and enter your admin password.

Don’t be alarmed if this takes a while to complete.

Now that you've erased your macOS disk, return to the Utilities window and select Reinstall macOS. Simply follow the onscreen instructions.

When you boot up your Mac, the error will be gone.

Although annoying, “the disk Macintosh HD can’t be unlocked” error is relatively easy to fix, and now you know how.