Repair Disk Permissions: What It Does & How to Run It

Repairing disk permissions fixes file and folder access rights on macOS, and it is only needed on older versions of macOS (10.10 and earlier). On modern macOS, the system automatically protects system files, so the manual repair tool is gone; you can use First Aid in Disk Utility instead.

What Disk Permissions Actually Are

Every file and folder on a Unix-based system like macOS has an access control list that defines who can read, write, or execute it. This list includes the owner, a group, and “others,” each with three possible permissions: read (r), write (w), and execute (x). For example, a system file might be owned by root, readable by everyone, but writable only by root. If those permissions get corrupted—say, a user accidentally changes the owner of a system folder—apps can crash, fail to launch, or behave unpredictably.

Disk permissions repair scans the system for files whose permissions do not match the expected values stored in a database, then resets them to the correct state. It does not touch your personal files or user data; it only checks files that Apple ships with macOS and some Apple applications.

Why Older Macs Needed It

Before OS X El Capitan (10.11), macOS did not fully protect its own system files from user modifications. If you installed a third-party app that wrote to a system folder, or if a software update went wrong, permissions could drift from the baseline. Symptoms included apps that would not open, printers that stopped working, or the system becoming slow to boot.

Apple provided two tools to fix this: Disk Utility’s “Repair Disk Permissions” and the command-line tool diskutil repairPermissions. Both compared the current permissions against a stored receipt of the original installation and restored any mismatches. This was a safe, non-destructive operation that rarely caused data loss.

What Changed in Modern macOS

Starting with OS X El Capitan (10.11), Apple introduced System Integrity Protection (SIP), a security feature that prevents even the root user from modifying protected system files. Because SIP blocks unauthorized writes at the kernel level, the permissions on those files can no longer be accidentally changed. As a result, Apple removed the Repair Disk Permissions option from Disk Utility and deprecated the diskutil repairPermissions command.

On current versions of macOS, the equivalent is First Aid in Disk Utility. First Aid checks the entire disk for file system errors, including permission inconsistencies, and repairs them automatically. It runs from the Recovery Mode or from the Disk Utility app when you boot normally.

How to Run First Aid (Modern Equivalent)

If you suspect permission issues on a modern Mac, run First Aid on your startup disk. Here is the process:

Open Disk Utility (in /Applications/Utilities).
Select your startup disk (usually named “Macintosh HD”) in the sidebar.
Click the “First Aid” button in the toolbar.
Click “Run” and enter your administrator password when prompted.
Wait for the process to finish; it may take several minutes.

If First Aid reports errors that it cannot fix, you may need to boot into Recovery Mode (hold Command+R at startup) and run First Aid from there. This is the recommended approach for serious disk issues.

Common Misconceptions and Mistakes

A frequent misunderstanding is that repairing permissions will fix all app crashes or slow performance. In reality, most app issues are caused by corrupted preferences, missing updates, or incompatible software—not permissions. Running First Aid on a healthy disk will show no problems, and it will not speed up your Mac.

Another mistake is using third-party “permission repair” tools that claim to fix permissions on modern macOS. These tools are unnecessary because SIP already prevents the underlying problem. Some may even cause harm by modifying system files in ways that Apple does not support.

Finally, do not confuse repairing permissions with erasing or reformatting. First Aid is non-destructive, but if you choose “Erase” in Disk Utility, you will lose all data. Always back up before doing any disk maintenance.

When You Might Still Need the Old Tool

If you are running an older Mac with OS X 10.10 Yosemite or earlier, the original Repair Disk Permissions can still be useful. You can access it by opening Disk Utility, selecting your startup disk, and clicking the “Repair Disk Permissions” button. Alternatively, you can use the Terminal command diskutil repairPermissions /.

On those systems, it is safe to run the repair periodically, especially after a major software update or after installing software that modifies system files. However, on any Mac running El Capitan or later, the command will return an error because the feature has been removed.

Alternatives for Troubleshooting

If you are experiencing symptoms that you think might be permission-related, try these steps before resorting to disk repair:

Restart your Mac in Safe Mode (hold Shift during boot) to force a directory check and disable unnecessary extensions.
Reset NVRAM (on Intel Macs) or SMC to fix low-level hardware settings.
Check for software updates in System Settings, as many bugs are fixed with patches.
If a specific app is failing, delete its preferences (in ~/Library/Preferences) and restart the app.
Run First Aid as described above—it is the only official disk repair tool on modern macOS.

For persistent issues, creating a new user account and testing whether the problem occurs there can help isolate whether the issue is system-wide or user-specific.

Frequently Asked Questions

Is repairing disk permissions safe?

Yes, on older macOS versions it was safe and non-destructive. On modern macOS, First Aid is equally safe. Neither tool deletes your personal files, but it is always wise to back up before any disk operation.

Why can’t I find “Repair Disk Permissions” in Disk Utility?

Because Apple removed it in OS X El Capitan (10.11) and later. The feature was replaced by First Aid, which handles both permissions and other file system errors.

Will repairing permissions speed up my Mac?

No. Permission repair only fixes access rights; it does not clear cache files, free up memory, or improve performance. If your Mac is slow, look for other causes like insufficient storage or too many startup items.

Can I repair permissions on an external drive?

On modern macOS, First Aid can be run on any connected volume, including external drives. On older macOS, the repair permissions tool only worked on the startup volume, not external disks.

Do I need to run First Aid regularly?

No. Unlike older versions, modern macOS automatically maintains system file integrity via SIP. Running First Aid is only necessary when you suspect a disk problem, such as after a crash or when the system behaves abnormally.

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.

More cards in this drawer

The whole Numbers and Powers drawer →