How to Fix External Hard Drive Not Mounting on Mac (2026 Guide)

Your external hard drive worked yesterday. Today, you plug it in and nothing happens. No icon on the desktop. No notification. Just silence.

This problem affects thousands of Mac users every week. The good news? Most external hard drive mounting issues have simple fixes you can do yourself in under 15 minutes.

This guide walks you through every proven solution, from quick checks to advanced repairs. We’ll start with the easiest fixes and work toward more technical solutions.

Why Your External Hard Drive Won’t Mount

Before jumping into fixes, understand what’s happening. When you connect an external drive, macOS needs to:

• Recognize the physical connection
• Read the drive’s file system
• Mount it as a readable volume
• Display it in Finder

A breakdown at any point stops the drive from appearing. Common causes include:

• Loose or damaged cables
• Corrupted file systems
• Outdated macOS drivers
• Power supply issues
• Physical drive damage
• Incompatible file formats

Now let’s fix it.

Quick Checks First (5 Minutes)

Start here. These simple tests solve about 40% of mounting problems.

Check the Physical Connection

Unplug the drive completely. Wait 10 seconds. Plug it back in.

Try a different USB port. Many Mac mounting issues come from port-specific problems, not drive failures.

If you’re using a USB hub, remove it. Connect the drive directly to your Mac. Hubs sometimes provide insufficient power for larger external drives.

Test the Cable

Cables fail more often than drives. Swap in a different cable if you have one. Look for visible damage like fraying or bent connectors.

For USB-C drives, cable quality matters significantly. Cheap cables lack proper power delivery.

Listen and Look

Put your ear near the drive. Do you hear it spinning up? A clicking sound means mechanical failure. A healthy drive makes a gentle whirring noise.

Check for a power light. If the drive has one and it’s not lit, you have a power issue.

Try Another Computer

Connect your external hard drive to a different Mac or PC. If it mounts there, the problem is with your Mac, not the drive. If it still doesn’t mount, focus on drive-level fixes.

Use Disk Utility to Mount the Drive

macOS includes Disk Utility, a powerful tool for managing storage. Many unmountable drives appear here even when Finder can’t see them.

Open Disk Utility

1. Click the Finder icon
2. Select Applications
3. Open the Utilities folder
4. Double-click Disk Utility

Or press Command + Space, type “Disk Utility,” and hit Enter.

Look for Your Drive

In Disk Utility’s sidebar, check under “External.” Your drive might appear grayed out or without its normal name.

Click View in the toolbar and select Show All Devices. This displays physical drives and their volumes separately.

Mount Manually

If you see your drive:

1. Select it in the sidebar
2. Click the Mount button in the toolbar
3. Wait 10-30 seconds

If mounting succeeds, your drive appears in Finder. Problem solved.

If you see “com.apple.DiskManagement.disenter error 0,” continue to the next section.

Run First Aid

First Aid scans and repairs file system errors.

1. Select your external drive
2. Click First Aid in the toolbar
3. Click Run
4. Wait for the scan to complete

This process takes 5 minutes to 2 hours depending on drive size. Let it finish completely.

If First Aid finds and fixes errors, try mounting again. Many users report success after this step.

Reset NVRAM/PRAM

Your Mac stores certain settings in NVRAM (non-volatile random-access memory). Corrupted NVRAM sometimes prevents drives from mounting.

For Intel Macs

1. Shut down your Mac completely
2. Press the power button
3. Immediately press and hold Option + Command + P + R
4. Keep holding for about 20 seconds
5. Release when you hear the startup sound twice (or see the Apple logo appear and disappear twice)

For Apple Silicon Macs

Apple Silicon Macs don’t use NVRAM reset the same way. Instead:

1. Shut down your Mac
2. Wait 30 seconds
3. Start it up normally

The system automatically checks and repairs certain settings on boot.

After restarting, reconnect your external hard drive.

Reset the SMC (Intel Macs Only)

The System Management Controller handles power and hardware connections. Resetting it fixes mysterious mounting problems.

MacBooks with Non-Removable Batteries

1. Shut down the Mac
2. Press and hold Shift + Control + Option on the left side of the keyboard
3. While holding those keys, press the power button
4. Hold all four keys for 10 seconds
5. Release everything
6. Press the power button normally to start

Desktop Macs

1. Shut down the Mac
2. Unplug the power cord
3. Wait 15 seconds
4. Plug the power cord back in
5. Wait 5 seconds
6. Press the power button

Apple Silicon Macs don’t have a separate SMC. The system manages these functions automatically.

Check for macOS Updates

Apple regularly fixes drive compatibility bugs in macOS updates.

1. Click the Apple menu (top-left corner)
2. Select System Settings (macOS Ventura/Sonoma) or System Preferences (older versions)
3. Click General then Software Update
4. Install any available updates

After updating, restart your Mac and test the external drive.

Repair with Terminal Commands

Terminal provides advanced disk repair tools. These commands work when Disk Utility fails.

Open Terminal

Press Command + Space, type “Terminal,” and press Enter.

List All Drives

Type this command and press Enter:

diskutil list

You’ll see all connected drives, even unmounted ones. Look for your external drive. Note its identifier (like “disk2” or “disk3”).

Force Mount

Replace “disk2” with your drive’s actual identifier:

diskutil mount disk2

If this works, the drive appears in Finder.

Repair the Drive

Try this repair command (replace “disk2”):

diskutil repairDisk disk2

Wait for completion. Then attempt mounting again.

Verify the File System

Run a verification check:

diskutil verifyDisk disk2

This reports file system problems without making changes.

Format the Drive (Data Loss Warning)

If nothing else works, formatting creates a fresh file system. This erases everything on the drive.

Only do this if:

• You’ve tried all other solutions
• You have backups elsewhere
• The drive contains no critical data

Formatting Steps

1. Open Disk Utility
2. Select your external drive (the top-level device, not a volume)
3. Click Erase in the toolbar
4. Choose a format:
   • APFS: Best for Mac-only use, macOS 10.13+
   • Mac OS Extended (Journaled): Compatible with older Macs
   • ExFAT: Works with both Mac and Windows
5. Name your drive
6. Click Erase

Wait for the process to finish. Your drive will mount automatically.

File System Compatibility Issues

Macs can’t natively write to NTFS drives (Windows format). They can read NTFS but not mount it for full use without additional software.

Check Your Drive Format

In Disk Utility, select your drive and look at the file system listed. Common formats:

Format	Mac Read	Mac Write	Windows Compatible
APFS	Yes	Yes	No
Mac OS Extended	Yes	Yes	No
ExFAT	Yes	Yes	Yes
FAT32	Yes	Yes	Yes
NTFS	Yes	No*	Yes

*Requires third-party software like Paragon NTFS or Tuxera NTFS for write access.

If you need Windows compatibility, reformat to ExFAT (erases data).

Advanced: Single User Mode Repair

When macOS itself has problems, Single User Mode provides direct system access.

1. Shut down your Mac
2. Press the power button
3. Immediately hold Command + S
4. Release when you see white text on black background
5. Wait for the command prompt
6. Type: fsck -fy and press Enter
7. Wait for “The volume appears to be OK”
8. Type: reboot and press Enter

Connect your external drive after restart.

Check for Hardware Failure

Sometimes drives fail physically. Warning signs:

• Clicking or grinding noises
• Drive not spinning up
• Burning smell
• Drive extremely hot to touch
• Repeated mounting failures across multiple computers

If you suspect hardware failure:

1. Stop using the drive immediately
2. Don’t attempt repeated repairs
3. Consider professional data recovery if files are critical
4. Services like DriveSavers specialize in failed drive recovery

Prevent Future Mounting Problems

Once your drive works again, take these steps:

Always Eject Properly

Never unplug an external drive without ejecting it first:

1. Right-click the drive icon
2. Select Eject
3. Wait for the icon to disappear
4. Then disconnect the cable

Improper ejection corrupts file systems.

Use Quality Cables

Replace cheap cables with certified ones. For USB-C, look for USB-IF certification. For Thunderbolt, buy cables from reputable brands.

Regular Backups

External drives fail. Keep important files in multiple locations:

• A second external drive
• Cloud storage (iCloud, Dropbox, Google Drive)
• Time Machine backups

Keep macOS Updated

Apple fixes drive compatibility bugs regularly. Enable automatic updates:

1. Open System Settings
2. Go to General > Software Update
3. Enable automatic updates

Monitor Drive Health

Use tools like DriveDx or built-in SMART status:

1. Open Disk Utility
2. Select your drive
3. Click Info button
4. Check “S.M.A.R.T. Status”

“Verified” means healthy. “Failing” means replace the drive soon.

When to Seek Professional Help

Contact Apple Support or a Mac specialist if:

• None of these solutions work
• Your drive contains critical, irreplaceable data
• You’re uncomfortable using Terminal
• The drive shows signs of physical damage
• You need same-day recovery

Apple’s support page offers additional resources at https://support.apple.com/.

Common Error Messages Explained

“The disk you inserted was not readable by this computer” The file system is corrupted or incompatible. Try First Aid or reformatting.

“com.apple.DiskManagement.disenter error 0” Permission or encryption problem. Try mounting through Terminal.

“The operation couldn’t be completed. Undefined error: 0” Generic failure message. Reset NVRAM and SMC, then try again.

“You can’t open the application because it may be damaged or incomplete” Wrong error for a drive issue, but appears sometimes. Eject and reconnect.

Summary and Quick Reference

Most Mac external hard drive mounting problems come from simple issues with quick fixes.

Start here:

1. Try different ports and cables
2. Open Disk Utility and click Mount
3. Run First Aid

If that doesn’t work: 4. Reset NVRAM 5. Reset SMC (Intel Macs) 6. Update macOS 7. Use Terminal diskutil commands

Last resort: 8. Format the drive (erases everything) 9. Check for hardware failure 10. Contact professional recovery

About 85% of mounting problems resolve with the first three steps. The remaining cases need deeper troubleshooting, but most are still fixable without professional help.

Conclusion

An external hard drive not mounting feels like a disaster. In reality, it’s usually a minor technical hiccup with a straightforward solution.

Start with the quick physical checks. Move to Disk Utility. Try the system resets. Most drives respond to one of these approaches.

If your drive still won’t mount after trying everything, the problem might be hardware failure. At that point, evaluate whether the data justifies professional recovery costs.

Remember to back up regularly. External drives are convenient but not permanent. Keep important files in multiple locations. That way, a mounting problem becomes a minor inconvenience instead of a crisis.