How to repair a disk on a Mac with Disk Utility First Aid

howtosimply.com/guides/how-to-repair-a-disk-on-a-mac-with-disk-utility-first-aid/ · Checked October 2026 · MacBook Neo · macOS 27.0.1

7 of 7 steps with real screenshots · 1 official source below

Device

Mac

Shown on

macOS 27.0.1 (MacBook Neo)

App

Disk Utility

Real screenshots

7 of 7 steps

Checked

October 2026

Sources

1 official, linked below

Step by step

1. 

   Open Disk Utility

   It is in Applications, Utilities. To repair the startup disk, or if the Mac does not start, open it from macOS Recovery: on a Mac with Apple silicon, shut down, press and hold the power button until Options appears, select Options and click Continue. Apple's Disk Utility article then says: when you see the list of utilities, select Disk Utility, then click Continue. On our MacBook Neo, Disk Utility opened with Macintosh HD volumes under Internal and an iOS 27.0 Simulator under Disk Images.

   Done

2. 

   Show all devices

   Choose View, Show All Devices in the menu bar, or use the View button at the left of the toolbar. On our MacBook Neo the View menu had a tick next to Show Only Volumes, and the sidebar showed Macintosh HD, its snapshot and Macintosh HD - Data. With all devices shown, the sidebar lists each disk with its containers and volumes indented below it (step 5).

   Done

3. 

   Start with the last volume

   Select the last volume listed under the disk, Macintosh HD - Data on our MacBook Neo. Click First Aid and then Run. Enter your administrator password if asked. Our MacBook Neo asked: Run First Aid on "Macintosh HD - Data"? First Aid will check the volume for errors. It will then repair the volume if necessary.

   Done

4. 

   For the startup disk, use Recovery

   Macintosh HD - Data is on the startup disk. On our MacBook Neo, clicking Run showed: Verifying the startup volume will cause this computer to stop responding. This may last for several minutes or hours. To avoid this, you can run First Aid while in Recovery. We clicked Cancel. Run First Aid on the startup disk from macOS Recovery, as in step 1.

   Done

5. 

   Work upwards

   When it is finished, select the next volume or group above it and click First Aid again. Skip the read-only snapshot. Go on in this order: all volumes, then each container, then the disk itself at the top. If the First Aid button is dimmed for an item, skip it. On our MacBook Neo, with all devices shown, the sidebar listed APPLE SSD AP0512Z Media, Container disk3, Macintosh HD volumes, Macintosh HD with its snapshot indented below it, and Macintosh HD - Data at the bottom. With Macintosh HD selected, it read APFS System Volume, Not Mounted and System Snapshot Mounted. First Aid sits between Volume and Partition in the toolbar.

   Done

6. 

   Read the result

   When First Aid is done, a sheet shows the result. Click Done. We ran First Aid on a 52,4 MB test disk image, HowToSimply Test, not on the startup disk. The sheet showed a green tick and First Aid process is complete. Click Done to continue. Show Details listed the checks and ended with Operation successful.

   Done

7. 

   Restart

   Quit Disk Utility and choose Restart… from the Apple menu.

   Done

If you do not see this option

• No containers or disks in the sidebar Our MacBook Neo opened Disk Utility showing volumes only. The View button at the left of the toolbar switches to Show All Devices.
• External drive missing With no external drive connected, our MacBook Neo lists only Internal and Disk Images in the sidebar. Connect the drive, check its cable and power, then look again.

If this does not work

• A snapshot is selected Our MacBook Neo opened with Macintosh HD snap… selected, a read-only APFS Startup Snapshot. Skip it and select the Macintosh HD volume above it instead (step 5).
• A simulator shows up as a disk Our MacBook Neo also lists iOS 27.0 Simulator under Disk Images. That is a disk image, not the internal disk.
• First Aid finds errors it cannot repair Apple's Disk Utility article: if Disk Utility found errors that it can't repair, use Disk Utility to erase (format) the disk. Erasing deletes everything on it, so back up first if you can. Source: How to repair a Mac storage device with Disk Utility

About this guide

First Aid checks the structure of a disk and repairs errors in it. It is the right tool when a Mac starts slowly or not at all, when files will not open, or when an external drive behaves oddly. Back up first if you can.

Screenshots: MacBook Neo, macOS 27.0.1, dark mode.

Good to know

If the disk does not appear in Disk Utility at all, Apple says the Mac or the drive might need service. First shut the Mac down, unplug all devices that are not needed, check the cable and power of an external drive, and try again.

Back up before the repair if the Mac still runs: how to back up a Mac with Time Machine.

Related: external drive not showing up on a Mac: 8 fixes to try and Mac starts up to a black screen: 5 fixes to try.

In short: Back up, Disk Utility, View, Show All Devices, First Aid on the last volume, then upwards through volumes, containers and the disk, restart.