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External Drive Won't Mount

The hardware showed up. The volume didn’t. Mount it, then let First Aid walk the disk from the inside out. Erase stays last, after you’ve copied what you can.

About 10 minutes · Tick the steps as you go

1. Mount the volume, not the outer device

Show All Devices again. Click the volume — the row with the name you expect in Finder — and Mount. Clicking the outer device and wondering why Mount does nothing is a classic mix-up.

If macOS asks for a password, that’s an encrypted volume doing its job. Mount comes after unlock.

View > Show All Devices. Select the volume, not the outermost hardware row. Click Mount. Wait. Large spinning disks are slow to appear the first time.

2. First Aid, from the last volume upward

First Aid checks the formatting and directory structure. It is not magic, and it wants a current copy of anything you care about before you lean on it.

The useful order is boring: start at the last volume on that device, run First Aid, then the item above it, and keep climbing — volumes, then a container if there is one, then the device itself. Don’t quit Disk Utility while a pass is running.

Select the last volume on the drive > First Aid > Run. When it finishes, select the next row up and run First Aid again. Keep going until you’ve checked the container (if any) and finally the device. If First Aid is dimmed on a row, skip that row and continue up.

If this were the internal startup disk you’d do this from macOS Recovery. For a USB disk, Disk Utility from /Applications/Utilities is the right tool.

3. When First Aid says it can’t fix it

That’s the moment to stop writing, not the moment to hit Erase out of frustration. Copy whatever still opens. Then decide if you even want this enclosure as a blank disk.

Stop copying new files onto it. Don’t empty the Trash onto it. Copy off anything that still reads, even if it’s slow. Only after that, use Before You Format the Drive.

Erase deletes everything on that volume. First Aid never promised to save a dying disk.

4. Mounts, then immediately vanishes

That’s often power or a cable that drops under load, not a format you can repair forever. See USB Drive Not Working or Disconnecting if it greys out while you copy.

Apple’s pages, if you want them: Repair a Mac storage device with Disk Utility

I wrote these lists from the same public Mac Help and Disk Utility notes everyone can read — in my own words, with the order I actually use. Apple’s pages are linked above if you want the official version.

Still stuck?

If this list didn’t get the drive back, write to me.

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