How To Fix “Disk Locked” When Reinstalling macOS

So you’re trying to reinstall macOS, maybe to fix a problem or give your Mac a fresh start… but when you get to the part where you pick your hard drive, it says “Disk Locked.”

That message looks scary, like your Mac is holding your data hostage. But don’t panic! It’s actually pretty easy to fix once you know what’s going on.

Let’s break it down step by step.

What “Disk Locked” Actually Means

Your Mac’s “disk” is basically its internal drive, where all your apps, photos, and files live.

When you see “Disk Locked,” it usually means one of three things:

1. The drive is encrypted (locked with a password)
2. The drive hasn’t been erased properly
3. The Mac doesn’t have permission to write new files on it yet

So in plain English: macOS wants to install itself there, but the drive is saying, “Nope, you don’t have the keys.”

Why It Happens

There are a few common reasons this pops up:

• You erased your drive the wrong way in Disk Utility
• You’re trying to reinstall macOS on a new or used Mac with leftover partitions
• The drive still has FileVault encryption turned on
• You wiped the drive using “Erase Volume” instead of “Erase Disk”

Basically, the Mac is confused about what’s allowed on that drive. But don’t worry — we’ll sort it out.

Step 1: Boot Into macOS Recovery

We’re going to use a special mode built into every Mac called macOS Recovery.

Here’s how to open it:

• Apple Silicon Macs (M1, M2, M3): Hold the Power button until you see “Loading startup options.”
• Intel Macs: Turn on your Mac and immediately press Command (⌘) + R until the Apple logo appears.

Once you’re in, you’ll see a window called macOS Utilities.

Step 2: Open Disk Utility

Click Disk Utility. This is the tool that lets you see and manage all the drives and partitions on your Mac.

When it opens, look at the top left and click View → Show All Devices.
This is super important! You want to see the entire drive, not just the volume.

You’ll notice something like this in the sidebar:

• Apple SSD (the whole disk)
   - Macintosh HD (volume)
   - Macintosh HD – Data (volume)

Step 3: Erase the Whole Disk (Not Just the Volume)

Here’s where most people go wrong. If you only erase the volume, macOS still thinks there’s leftover stuff on the drive.

You need to:

1. Select the top level drive (the one with the hardware name, like Apple SSD).
2. Click Erase at the top.
3. Choose the following settings:
    - Name: Macintosh HD
    - Format: APFS
    - Scheme: GUID Partition Map

Then click Erase again.

This will completely wipe the drive and remove the lock.

(If it asks for a password, that’s your old FileVault password. Enter it to unlock the disk before erasing.)

Step 4: Reinstall macOS

When the erase finishes, close Disk Utility.
Now, in the main macOS Utilities window, click Reinstall macOS and follow the steps.

Choose your freshly erased Macintosh HD as the install location.

Boom, no more “Disk Locked.”

Step 5: If It Still Says Locked…

Okay, if you still get the locked message, try these extra steps:

Option 1: Use Terminal in Recovery Mode

1. In the top menu, click Utilities → Terminal
2. Type: diskutil list This shows all disks. Find your main drive (usually disk0).
3. Then type: diskutil eraseDisk APFS MacintoshHD disk0 Replace disk0 if your drive has a different name.
   That command fully wipes and reformats the drive.

Option 2: Reset NVRAM (Intel Macs only)

1. Turn off your Mac.
2. Hold Option + Command + P + R while turning it back on.
3. Keep holding for 20 seconds, then release.

Now try again — most of the time, this clears the “locked” issue.

Step 6: Reinstall macOS Again

Once the drive is erased and unlocked, reinstall macOS as usual.

If your Wi-Fi is on, macOS will download the latest version that’s compatible with your device.
When it’s done, your Mac will boot up like it’s brand new, no more lock, no more stress.

Bonus Tip: Avoid the Problem Next Time

If you ever plan to erase your Mac again, like when selling it or reinstalling macOS, always:

• Erase the whole drive (not just the volume)
• Use APFS and GUID Partition Map
• Make sure FileVault is turned off before you start

You can check FileVault under System Settings → Privacy & Security → FileVault.

Quick Recap

• “Disk Locked” means your drive can’t be written to.
• The fix is erasing the entire disk, not just one part of it.
• Use Disk Utility in Recovery mode, reformat with APFS, and reinstall macOS.
• If that doesn’t work, use Terminal to erase it manually.

The Bottom Line

When your Mac says “Disk Locked,” it’s not broken, it’s just being cautious.
Once you know how to unlock and reformat the drive, reinstalling macOS is easy.
Think of it like giving your Mac a clean slate, all fresh, all yours again.