First Aid process has failed: what to do next, on the Mac's disk or an external one

Disk Utility runs First Aid and ends with First Aid process has failed. That means it found problems it could not fix. The disk may still work. The priority is making sure your files are safe before trying anything else.

1. Back up now

If the disk still mounts, copy what matters to another drive, or run a Time Machine backup. Every repair attempt after this is safer with a copy.

2. Read what it found

Click Show Details in Disk Utility, or run the check in Terminal, which prints the same messages:

diskutil verifyVolume /Volumes/YourDrive
# the Mac's own disk
diskutil verifyVolume /

3. Try again from Recovery

For the Mac's own disk, First Aid works better when macOS is not running from it. Start up in macOS Recovery (on Apple silicon, hold the power button at startup), open Disk Utility, choose View, Show All Devices, and run First Aid on each volume, then the container, then the disk.

4. External drive: copy off and erase

If First Aid keeps failing on an external drive, copy everything you can to another drive, then erase it in Disk Utility. A clean format usually works well afterwards. If errors return soon after, the drive itself is failing.

5. The Mac's own disk: reinstall or erase

If Recovery cannot repair the internal disk, reinstalling macOS from Recovery keeps your files and replaces the system. If problems persist, erasing and restoring from a backup is the clean fix. Reinstalling macOS covers the options.

Related: disenter error, Couldn't modify partition map and Disk Not Ejected Properly on Mac.