"First Aid process has failed" in Disk Utility: what to do next

30 October 2026 · 6 min read

Disk Utility ends a repair with “First Aid process has failed. If possible back up the data on this volume. Click Done to continue.” It means First Aid found damage in the drive’s file system and couldn’t fix it. The files are often still readable, so copy what matters to another drive before you try anything else. Then work out whether the damage is in the file system or in the drive itself.

What the message means

First Aid checks the structures a drive uses to keep track of your files: the volume, the container that holds it, and the partition map. When it finds an inconsistency it tries to correct it. “Failed” means a correction wasn’t possible, or the check couldn’t finish.

That is not the same as the drive being dead. A damaged file system often still lets you open and copy files. For a disk macOS has mounted in a limited state, a related message says “You can still open or copy files on the disk, but you can’t save changes to files on the disk. Back up the disk and reformat it as soon as you can.” Treat the First Aid failure the same way: read now, repair later.

The window has a Show Details button. Open it before you click Done. The log lists each check and the line where it stopped, which is useful if you ask for help or need to tell a bad cable from bad data.

Copy your data off first

Every further repair attempt writes to a drive that is already in trouble. Back up before you retry.

1. If the drive still appears in Finder, drag the folders you can’t replace to another disk with enough room.
2. If it doesn’t mount, select it in Disk Utility’s sidebar and click Mount. If Mount is dimmed or fails, a data recovery service is the next step, not another round of First Aid.
3. Copy the most important files first (photos, documents, project folders), then the rest.

If this is your Mac’s own startup disk and it still boots, a current Time Machine backup is what you want. Restoring a Mac from a backup explains what to expect when you need it.

Run First Aid in the right order

Apple’s instructions work upward through the sidebar, so the order matters. In Disk Utility, choose View, then Show All Devices if it’s available.

1. Select the last volume on the device and click First Aid, then Run. If the button is dimmed, skip that item.
2. Enter an administrator password if asked to unlock the disk.
3. When that check finishes, move up the list: run First Aid on each volume in turn, then on the container that holds them.
4. Finish with the device itself, the top entry for the physical drive.

Carry on up the list even if one step fails, once your files are safe. The log from each level shows where the damage is, which matters if you end up asking for help.

The startup disk needs Recovery

Disk Utility can check the disk macOS is running from, but it can’t repair it while it’s in use. When it finds damage there, it says so: “First Aid found corruption that needs to be repaired. To repair the startup volume, run First Aid from Recovery.” For the startup disk, or a Mac that won’t start all the way, start up from macOS Recovery, choose Disk Utility and click Continue. In Apple’s example the last volume, where you start, is Macintosh HD - Data, so the data volume gets checked as well as Macintosh HD. macOS Recovery explained covers how to get there on your type of Mac.

File system damage or failing drive

The repair log can’t always tell you which one you have. These clues can.

Check the health status. In Terminal, run:

diskutil info disk0

Look at the SMART Status line. On this Mac’s internal drive it reads “Verified”. The same value is in System Information: choose Storage and read “S.M.A.R.T. Status” under the drive. If it reads “Failing”, the drive’s own self-test reports a fault: copy your files off and replace it. External drives often report “Not Supported” because the enclosure doesn’t pass the data through, and that says nothing either way.

Watch for hardware symptoms. Clicking or grinding noises, a drive that disappears and reappears, or very slow copying with read errors point to hardware. Try a different cable and port first, and plug into the Mac directly rather than through a hub.

Consider how it got damaged. A drive unplugged without ejecting, a power cut or a crash during a write usually leaves file system damage and a healthy drive. Disk not ejected properly explains how that happens.

If First Aid keeps failing

When Disk Utility finds errors it can’t repair, Apple’s advice is to erase (format) the disk. Erasing deletes everything on it, so do it only after your files are safe elsewhere. Then restore from your backup.

• Damaged file system, healthy drive: erase, reformat and reuse it. Keep a second copy of anything important on it from now on.
• Failing drive: replace it. Reformatting a dying drive gives you a clean drive that fails again.

If the drive doesn’t appear in the sidebar at all, shut down, unplug everything that isn’t essential and try again. For an external drive, check the cable, the connections and the power.

What not to do

Don’t run First Aid over and over hoping the next pass works. Don’t install a third-party repair tool on the failing drive, because installing writes to it. Don’t erase before you’ve confirmed your files are copied somewhere else.

Questions

Can I still get my files after “First Aid process has failed”? Often yes. The message means the file system has damage that Disk Utility couldn’t repair, not that the files are gone. Try to mount the drive and copy files off it right away. If it won’t mount, a data recovery service is safer than repeated repair attempts.

Does “First Aid process has failed” mean the drive is dying? Not necessarily. It usually means file system damage, which an unsafe unplug or a crash can cause. Check the SMART Status with diskutil info, listen for clicking, and watch for a drive that disappears. Those point to hardware failure.

Why does First Aid fail on Macintosh HD? Disk Utility can check the disk macOS is running from but can’t repair it while it’s in use, so it tells you to run First Aid from Recovery. Restart into macOS Recovery, open Disk Utility there and run First Aid on each volume, then the container, then the drive. Start with Macintosh HD - Data.

Should I erase the disk? Only when your files are safely copied elsewhere and First Aid can’t repair it. Erasing removes everything on the drive. If the SMART Status says Failing, replace the drive instead of reformatting it.