How to Fix “The Disk Macintosh HD Can’t Be Unlocked” Error on Mac?

If you’re here, this is probably how it went down. You update macOS, restart, type in your password and instead of your desktop, up comes a gray box: “The disk ‘Macintosh HD’ can’t be unlocked. A problem was detected with the disk that prevents it from being unlocked.” You click OK. It disappears. Everything seems normal. Then you restart, and the same warning comes back.

Before anything else, the part worth knowing is that your Mac is almost certainly fine, and so are your files. The message reads like your startup disk is failing but that is rarely what’s happening. What’s happening instead is that macOS is trying to interact with a spare volume left behind during the update – often a duplicate with a name like Macintosh HD – Data – Data. In most cases the underlying storage device is healthy, and the issue affects how macOS reaches the volume rather than the files themselves.

You might also see this worded as “Macintosh HD – Data can’t be unlocked.” And there’s a rarer version where the Mac won’t boot at all, or asks for a password you don’t recognize. That points to a different issue which we’ll cover separately. Before moving on to the solution – identify exactly which version of the issue you’re dealing with.

Why This Happens

The “Macintosh HD can’t be unlocked” error means macOS can’t mount or decrypt one of the volumes on your startup disk. Most of the time a macOS update is to blame – it leaves behind an extra APFS Data volume, but FileVault problems, file-system corruption, or an incomplete macOS installation can produce the same message. Here’s how the main causes compare:

Can You Still Use Your Mac?

The “Macintosh HD can’t be unlocked” error shows up in two very different situations – and the correct fix depends entirely on which one you’re facing. Identify your scenario below before trying anything to determine which step to follow and which one to avoid.

Situation 1: Your Mac Works Normally, But the Error Keeps Returning

You can log into and operate your Mac normally. The alert displays almost immediately upon boot-up, goes away once you click “OK” and returns again the very next time you reboot. This happens more than all other cases combined and likely indicates that an older macOS update created a leftover or duplicate volume.

Go to Fix 1: Remove the Duplicate Volume

Situation 2: Your Mac Won’t Start Up, or asks for A Password You Don’t Have

Your Mac can’t get past the login or startup screen, keeps looping back to it, or requests a FileVault password or recovery key you no longer have. Your data is still on the drive and remains encrypted but getting back in means working through the repair steps in Fix 2 in order, starting with the safest.

Go to Fix 2: When Your Mac Won’t Boot

Fix 1: Remove the Duplicate Volume

Here’s an easy explanation of the situation. A recent macOS software update created a “Data” Volume for you but it left behind another Volume (empty) called “Data”. This was forgotten by the update process. As soon as you turn on your Mac, it will try to access this extra Volume and since there are no files or data stored here; it will fail each time and show you an error message when you start your Mac. The good news is your actual files/data have been safe all along in the first “Data” Volume. To fix the problem, you simply need to locate the empty Volume and delete it. The only part of this solution that requires some thought/attention is ensuring you are deleting the correct Volume (the empty one).

We’ll do this from macOS Recovery, where nothing is running off your disk and the volumes hold still long enough to tell apart.

1. Find the Leftover Volume

First boot into Recovery and open Disk Utility:

• Intel Mac: Restart and immediately hold Command + R until the Apple logo appears.
• Apple Silicon (M1 or newer): Shut the Mac down completely. Press and hold the power button until you see “Loading startup options”. Click Options > Continue. Select your user and enter the password if prompted.

In the Recovery window, open Disk Utility, then click View > Show All Devices in the top-left corner. You’ll now see your internal drive and every volume on it.

Look for two volumes with nearly identical names, usually “Macintosh HD – Data” plus a second one called something like “Macintosh HD – Data – Data,” or two volumes both named “Macintosh HD – Data.” One of them is the leftover. Here’s the reliable way to tell which is which:

• The one you keep holds your stuff. Click each volume and check its Used space. Your real Data volume will show a large amount used (your files, apps, and photos, usually tens or hundreds of GB). 
• The one you delete is the empty copy. The leftover shows little to no used space (at or near zero).

2. Delete the Leftover Volume

Once you’re certain you’ve selected the empty leftover:

• With that volume selected, click the minus (–) button in the Disk Utility toolbar or right-click the volume and choose Delete APFS Volume
• Confirm when prompted
• Quit Disk Utility and restart from the Apple menu

Fix 2: When Your Mac Won’t Boot

This situation is much worse than the recurring error message for the previous repair. Instead of receiving an error message, you’ve been locked out of the Mac completely. Here again, “lock” doesn’t equate with deleting; your files remain intact on the hard drive (FileVault encrypted) in exactly the same condition as it existed when everything broke down. Most commonly, what’s usually damaged is that part of the OS residing on the Data volume containing your files, images and applications. Below are the repairs listed from least risk to most severe.

Work top to bottom. Everything is safe to try until the very last step, and you’ll know clearly before you reach any method that actually erases your data. There are two exceptions to the top-to-bottom rule. If your wall is a password prompt rather than a boot loop, the problem is authentication, not the disk: jump straight to Step 3. And if your Mac is so far gone, it won’t even load Recovery, your options depend on whether you have an Intel or Apple Silicon Mac: go to Step 5.

1. Is Your Mac Asking for a Password or Recovery Key?

If you have been sent here from “Fix 2” and therefore did not run First Aid or Reinstall macOS first, then you will only be performing these steps. You can perform some basic troubleshooting prior to trying to resolve the issue.

Ensure that caps lock has been disabled on your computer. If you are always using a Non-U.S. Keyboard Layout – try entering your password in U.S. Keyboard Layout. The operating system may load the login screen before it loads your chosen keyboard layout when the operating system starts up.

Try to reset your password with your Apple ID. If you fail to log in to your computer several times, macOS will give you a “reset password” option using your Apple ID. You should be able to do this because you selected the option to use your iCloud account for FileVault recovery when you turned on encryption.

Use your FileVault recovery key. If you elected to have a FileVault recovery key instead of an Apple ID based recovery method – you will need to enter that key to unlock the disk. Your recovery key is 24 characters long, arranged into six groups of four characters per group. Check where-ever you saved it during the time that you configured FileVault such as a password manager, or a secure note, photo etc.

2. Run First Aid from Recovery

First Aid runs a diagnostic of the file system on your hard drive to see if there are any damaged files or directories. and also fixes them if possible. To do a full diagnostic run First Aid on all APFS volumes individually before running it on the container, and finally run it on the physical disk. It could take some time to get through all of these levels depending on how many layers your hard drive contains, but it’s probably the safest and fastest thing you can try first and may resolve most issues related to an interrupted software update. 

• Boot into macOS Recovery
• Log in to your user profile
• Click Options and hit Continue
• Open Disk Utility 
• Click View > Show All Devices 
• Run First Aid on the items under your internal drive

Start from the bottom of the list and work your way up: each volume first, then the container, then the disk itself. If First Aid reports that it found and repaired errors, restart and see if the Mac boots. If it can’t complete the repair, don’t run it over and over and move to the next fix.

3. Reinstall macOS (Without Erasing Anything)

Your startup disk is split into two separate volumes – a sealed system volume that holds macOS itself and the Data volume which holds everything else. A botched update corrupts the system half and reinstalling macOS from Recovery rewrites only that half. This is not an erase. Your files, apps, and settings ride along untouched and it’s the single most reliable fix for a Mac that stopped booting after an update.

• Boot into macOS Recovery
• Log in to your user profile
• Click Options and hit Continue
• Select Reinstall macOS Tahoe and click Continue
• Follow the prompts and select Macintosh HD when asked where to install
• Let the process complete

When it finishes, you should land back at your normal login, with everything where you left it.

4. Secure Your Data Before Taking More Aggressive Measures

If the Mac boots up but files appear missing after the volume becomes accessible, recover them before making further repairs. Run a Mac Data Recovery Software on an external drive or a second Mac, scan the affected volume, and recover your files to a different drive. Since the volume is now unlocked and available, the software can search it end to end for files that disappeared during the failed update.

The Mac Still Won’t Boot, But You Can Unlock the Disk

If you have access to either the login password for the computer or the FileVault recovery key, you will likely have enough time to move all of your personal files to a safe location prior to taking on any repair options.

On an Apple Silicon Mac, boot into macOS Recovery, select Utilities > Share Disk, and connect the two Macs with a USB, USB-C, or Thunderbolt cable. The shared disk shows up on the healthy Mac in Finder, under Network in the sidebar.

For Intel Macs, start the Mac in Target Disk Mode by holding T while it is starting up, and connect the two Macs with a Thunderbolt or USB-C cable. Here the disk mounts on the healthy Mac like an ordinary external drive. Either way, unlock the disk from the healthy Mac (if prompted) and copy any data that you wish to save.

Once you are able to successfully unlock the disk and find out that some of your files are missing or were corrupted, you can run a recovery scan on the non-booting Mac’s drive from the healthy Mac. 

No Password or Recovery Key Available

Without valid credentials, the encrypted volume remains inaccessible. None of the current recovery Utilities are capable of bypassing FileVault encryption. As such, there is nothing to recover at this point. Therefore, when moving forward with the next step, please consider that all Data contained within the encrypted volume will likely be irretrievable.  

5. If Your Mac Won’t Load Recovery at All

Everything above assumes you can at least get into macOS Recovery. If that isn’t an option for you, uour options will be based on what kind of system you have.

On an Intel Mac: Target Disk Mode runs off the firmware level so it works even when Recovery won’t load. Hold T at startup, connect to a healthy Mac as described in Step 4 and transfer all data before trying any other solution.

On an Apple Silicon Mac: Share Disk lives inside Recovery so it isn’t an option when Recovery won’t start. But Apple Silicon Macs do include a fallback Recovery environment that may allow you to still load the primary recovery environment if the first one fails. To reach it: shut down the machine, press and release the power button then immediately press and hold it until you see the startup options menu. If that gets you into Recovery return to Step 1 and continue from there.

If even that doesn’t work – the next DIY solution is a DFU Revive using Apple Configurator. Install Apple Configurator on a second Mac from the Mac App Store. Connect the two machines with a USB-C cable and follow Apple’s model-specific steps to put the unresponsive Mac into DFU mode. Choose Revive Device: a Revive reinstalls both the firmware and the recovery system without touching your data. Watch the wording carefully in Apple Configurator, choose Revive, not Restore, because Restore erases the entire drive. After a successful revive, the Mac can usually load Recovery again, and you can resume from Step 1. If a revive fails too, hand the machine to Apple Support or an authorized service provider rather than experimenting further.

6. Erase and Reinstall macOS

As the last resort for the “Macintosh HD can’t be unlocked” error, erase the startup disk and then reinstall macOS. To be precise about what removes your data: the reinstall itself doesn’t erase anything (see Step 2) — it’s the erase step below that wipes the Macintosh HD volume before a fresh copy of macOS goes on, clearing whatever was preventing the disk from mounting or unlocking. Everything stored on the drive: personal docs, apps, and settings are removed in the process. If you copied your files to another disk via Share Disk or Target Disk Mode in Steps 4–5, double-check that backup now. If you reached this step without a password or recovery key, there is unfortunately nothing on the encrypted volume that can be saved first.

• Boot into macOS Recovery (Command + R at startup on Intel; on Apple Silicon, hold the power button, click Options > Continue, then select your user and enter your password)
• Open Disk Utility and click View > Show all devices
• Select Macintosh HD and click Erase
• Specify the name as Macintosh HD and the format as APFS
• Click Erase. If Disk Utility shows an Erase Volume Group button instead, click that. It removes Macintosh HD and its paired Data volume together in one correct step
• Only after the erase finishes, remove any extra leftover volumes still listed under the internal drive (such as a duplicate Macintosh HD – Data) using the (-) button — check each volume’s name and used space before deleting it, exactly as in Fix 1, so nothing is removed by mistake
• Quit Disk Utility once done and return to the Utilities window
• Reinstall macOS, click Continue and follow the on-screen instructions

Summing Up

The “Macintosh HD can’t be unlocked” message may look serious, but most times, this does NOT mean that your main drive (Macintosh HD), will fail or that you’ll lose ALL your files. The issue is more likely due to an old volume left over by a recent macOS update, a damaged System Install – or an issue with FileVault authentication. Identify which problem you are experiencing so you know how best to proceed. The initial steps would include eliminating duplicate volumes, performing First Aid on your Disk, or reinstalling macOS without erasing your data. If your Mac still won’t boot, prioritize securing your files before attempting more drastic repairs.