What First Aid can repair
First Aid checks a storage device's formatting and directory structure and attempts repairs. Apple lists corrupted files, unexpected app quits, external-device problems and startup failures among symptoms that can justify a disk check. Those symptoms also have other causes.
This is a targeted troubleshooting tool. It doesn't remove downloaded files, clear every cache or guarantee a speed improvement. It cannot repair every disk problem, and a successful check isn't a complete hardware diagnosis.
If Disk Utility says a disk is about to fail, Apple's guidance is to back up the data and replace it. Repeating First Aid doesn't make failing storage dependable.
Before you start
Make a current backup of important files if the disk is readable. Apple recommends a backup because damaged files or unrepairable errors may require recovery later. If this is your only copy of irreplaceable data and the device is failing or unreadable, get recovery advice before escalating to erasing it.
Save open work. Identify the storage device you intend to check: an external drive, the internal startup disk, or a volume inside one of them. Several similarly named entries can belong to the same device.
For an external drive, connect it reliably and check that it has power. If several external drives have similar names, confirm the connection and capacity before selecting one. First Aid and Erase are different buttons; this procedure uses First Aid.
Open Disk Utility in the right environment
For an external or other non-startup device, open Applications › Utilities › Disk Utility. You can find it with Spotlight as well.
For the startup disk, or if the Mac doesn't finish starting, use Recovery:
- Shut down the Mac. On Apple silicon, press and hold its power button until startup options appear, then choose Options › Continue.
- On an Intel Mac, turn it on and immediately hold Command-R to enter built-in Recovery.
- Follow the onscreen account or disk-unlock prompts yourself. Select Disk Utility in the Recovery utilities window, then click Continue.
The complete chip-specific route and alternatives are in the Recovery guide. Internet Recovery keyboard shortcuts are Intel-specific; don't use them as the normal Apple silicon sequence.
Show volumes, containers and the device
In Disk Utility choose View › Show All Devices. The sidebar shows the hierarchy rather than only mounted volumes. Expand disclosure arrows so the entries under the intended device are visible.
| Level | What it represents | Order |
|---|---|---|
| Volumes and volume groups | Named storage areas, such as Macintosh HD and Macintosh HD - Data | First, from the bottom upward |
| APFS container | A shared storage pool containing volumes | After its volumes |
| Physical device | The drive at the top of that hierarchy | Last |
Names and the number of entries differ. Not every filesystem has a container or volume group. Follow your sidebar rather than expecting a screenshot's disk number to match. On a startup disk, include the data volume as well as the system volume.
Run First Aid from the bottom upward
- Select the last volume listed under the device you're checking.
- Click First Aid, then Run or Repair Disk. Follow the onscreen instructions. If asked to unlock an encrypted disk, enter the administrator password on your own Mac.
- When the check finishes, read the result and click Done.
- Select the next volume or volume group above it and repeat.
- Check each container after its volumes, then check the physical device last.
If First Aid is dimmed for an entry, Apple says to skip that entry. Don't substitute Erase simply because the repair control is unavailable.
Allow the operation to finish. There is no universal completion time: the device, filesystem and errors differ. Record the actual result or error message rather than describing every long check as frozen.
Read the result before choosing the next step
If the check succeeds, finish the remaining levels and restart normally if you used Recovery. Try the task that originally failed. A clean filesystem result narrows the investigation; it doesn't establish that the original app, cable or hardware is healthy.
If errors were repaired, test again and keep backups current. If an error remains, follow Apple's repair guidance. Its next steps can include erasing and reformatting a device, which deletes data. That is a separate decision requiring a usable backup or a recovery plan, not another harmless repair click.
For a startup failure that persists after the disk check, see the Apple-logo guide or the blank-screen guide. Reinstalling macOS without erasing is distinct from formatting a disk.
If the device is missing or cannot be repaired
Confirm Show All Devices is selected. For external storage, check its cable, connection and power, then follow the manufacturer's connection guidance. If Disk Utility still can't see it, Apple says the storage device or Mac may need service.
If the drive reports impending failure, prioritize a backup and replacement. If a repair cannot recover needed data, pause before erasure. A new empty filesystem will not preserve the only copy of files you hoped First Aid would recover.
These are documented steps, not a repair performed for this article. For the broader order of software checks and the tools each task uses, see Tend's Mac maintenance guide.
Questions
Does Disk Utility First Aid delete files?
First Aid checks and attempts to repair filesystem structures; it is separate from Erase. Apple still recommends a current backup because files may already be damaged or errors may be unrepairable. Erasing afterward deletes data.
Should I run First Aid on Macintosh HD or Data?
Include both volumes, any other volumes and volume groups on that device, then its containers and the physical device. Start at the bottom of the sidebar and work upward.
Do I need Recovery for First Aid?
Use macOS Recovery when checking the startup disk or when the Mac does not finish starting. Other connected devices can be checked from Disk Utility in the running system.
Can First Aid repair a failing disk?
No. Apple says that if Disk Utility reports a disk is about to fail, back up the data and replace it. First Aid cannot repair every disk problem.
Related guides
Mac maintenance
Choose a tool for the actual symptom.
Open Recovery
Use the sequence for your chip.
Safe mode
Investigate software startup issues.
SMC and NVRAM
Understand the Intel-specific resets.
Sources
- Apple, Disk Utility First Aid order and limits
- Apple, Repair steps and failing-drive warning
- Apple, Show the storage hierarchy
- Apple, Start up from macOS Recovery
- Apple, Back up with Time Machine
- Apple, Erasing is a separate destructive operation
- Apple, Reinstall macOS from Recovery
Choose the right maintenance task
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