How to Fix a Mac External Hard Drive Not Mounting: 2026 Guide

Your external hard drive worked fine yesterday. Today, you plug it into your Mac and nothing happens. No icon on the desktop, no prompt, no recognition whatsoever. This frustrating situation has multiple causes, but nearly all of them have solutions you can implement yourself.

This guide walks you through every proven method to fix an external hard drive that won’t mount on Mac, from simple cable checks to advanced disk repair techniques. Most issues resolve within 15 minutes using the steps below.

Why Your External Hard Drive Isn’t Mounting

Before jumping into fixes, understanding the root cause helps you avoid wasted time. External drives fail to mount for several reasons:

Hardware problems account for roughly 40% of mounting failures. A damaged USB cable, faulty port, or insufficient power delivery prevents your Mac from establishing a connection. Physical damage to the drive itself also falls into this category.

File system corruption represents another common culprit. If your Mac shut down unexpectedly while the drive was connected, or you removed the drive without ejecting it properly, the file system catalog may have become corrupted. Your Mac sees the drive but can’t read its directory structure.

Incompatible formatting stops drives formatted with certain file systems from mounting. While Macs read NTFS drives, they mount them as read-only by default. Drives formatted with Linux file systems like ext4 won’t mount without additional software.

Software conflicts occasionally interfere with mounting. Outdated macOS versions, problematic third-party security software, or corrupted system files can all prevent external drives from appearing.

Quick Checks Before Advanced Troubleshooting

Start with these simple diagnostic steps. They take less than five minutes and solve approximately 30% of mounting issues.

Test the Physical Connection

Unplug your external hard drive completely. Wait 10 seconds, then reconnect it to a different USB port. If you were using a USB hub, connect the drive directly to your Mac instead. Hubs sometimes provide insufficient power for drives that don’t have separate power adapters.

Listen for the drive spinning up when you connect it. Most mechanical hard drives make an audible whirring sound. If you hear clicking or beeping instead, the drive likely has hardware failure requiring professional data recovery.

Check the cable thoroughly. USB cables fail more often than people realize. If you have another cable compatible with your drive, swap it out. For USB-C drives, try a different USB-C cable rated for data transfer, not just charging.

Verify Power Supply

External drives with 2.5-inch mechanisms usually draw power from the USB connection alone. Larger 3.5-inch drives almost always need external power adapters. Confirm the power adapter is plugged in, the outlet works, and any power switch on the drive enclosure is turned on.

Some high-capacity portable drives require more power than a single USB port provides. If your drive came with a Y-cable (a USB cable that splits into two connectors), plug both connectors into your Mac.

Check Finder Preferences

Your drive might be mounting successfully but not showing up because of Finder settings.

Open Finder, then click Finder in the menu bar and select Preferences. Click the General tab. Ensure External disks is checked. Also check the Sidebar tab and verify External disks is selected under Locations.

If these boxes were unchecked, your drive is probably working fine but just hidden from view.

Use Disk Utility to Mount the Drive Manually

Disk Utility is macOS’s built-in tool for managing storage devices. It often detects drives that don’t appear in Finder.

Access Disk Utility

Press Command + Spacebar to open Spotlight Search. Type “Disk Utility” and press Enter. Alternatively, navigate to Applications > Utilities > Disk Utility.

In Disk Utility’s sidebar, look for your external drive. If it appears grayed out or unmounted, you’re in the right place. If it doesn’t appear at all, skip to the hardware troubleshooting section below.

Mount the Drive

Select your external drive from the sidebar. Click the Mount button in the toolbar at the top of the window. If mounting succeeds, the drive should appear in Finder within seconds.

If the Mount button is grayed out or you receive an error message, note the exact error text. Common errors include “com.apple.DiskManagement.disenter error 49244” (indicating APFS corruption) or “could not mount disk” (often related to file system damage).

Run First Aid

Disk Utility’s First Aid feature repairs common file system problems that prevent mounting.

Select your external drive in the sidebar. Make sure you select the volume name (indented beneath the physical disk), not just the top-level disk entry. Click First Aid in the toolbar, then click Run in the confirmation dialog.

First Aid typically takes 5-30 minutes depending on drive size. The utility scans the file system structure, checks for errors, and attempts repairs automatically. If First Aid finds and fixes problems, try mounting the drive again afterward.

If First Aid reports “underlying task reported failure” or cannot repair the volume, the corruption exceeds what this tool can handle. Proceed to terminal commands below.

Terminal Commands for Stubborn Drives

When Disk Utility fails, command-line tools often succeed. These commands access lower-level disk management functions.

List All Disks

Open Terminal from Applications > Utilities > Terminal. Type the following command and press Enter:

diskutil list

This displays all storage devices connected to your Mac, including unmounted drives. Look for your external drive by capacity or name. It will have an identifier like /dev/disk2 or /dev/disk3. Note this identifier for the next steps.

Force Mount Using diskutil

Replace disk2 in the command below with your actual disk identifier:

diskutil mount /dev/disk2

If successful, you’ll see a confirmation message and the drive will appear in Finder. If this fails, try mounting the specific volume instead of the whole disk:

diskutil mount /dev/disk2s1

The s1 refers to partition 1 on the disk. If your drive has multiple partitions, try s2, s3, and so on.

Repair from Terminal

For more aggressive repair attempts, use the fsck (file system consistency check) command. First, identify your disk using diskutil list as shown above.

If your drive uses APFS (common on newer drives formatted by Macs):

diskutil apfs unlockVolume /dev/disk2s1

Then run:

fsck_apfs -y /dev/disk2s1

For HFS+ formatted drives:

diskutil unmount force /dev/disk2s1
fsck_hfs -fy /dev/disk2s1

These commands can take considerable time on large drives. The -y flag automatically answers “yes” to repair prompts. When complete, try mounting again with diskutil mount.

Handle File System Compatibility Issues

Macs support multiple file systems natively but treat others as read-only or ignore them entirely.

Understanding Mac File System Support

macOS reads and writes to APFS (modern Mac format), HFS+ (older Mac format), FAT32, and exFAT without additional software. It can read but not write to NTFS (Windows format). Linux formats like ext4 or btrfs require third-party drivers.

To check your drive’s format, look in Disk Utility. Select the drive and check the details in the information panel. If it shows NTFS and you need write access, you have three options:

1. Reformat the drive (erases all data)
2. Install commercial software like Paragon NTFS
3. Enable experimental NTFS write support in macOS (not recommended due to reliability issues)

Reformat the Drive

Warning: Reformatting erases everything on the drive. Back up data first if possible.

In Disk Utility, select the external drive (the top-level disk entry, not the volume beneath it). Click Erase in the toolbar. Choose APFS for modern Macs (macOS 10.13 or later) or Mac OS Extended (Journaled) for older systems. If you need Windows compatibility, choose exFAT.

Name the drive, then click Erase. The process typically completes in under one minute. Afterward, the freshly formatted drive should mount immediately.

Reset NVRAM and SMC

System-level settings occasionally interfere with drive recognition. Resetting NVRAM (non-volatile random-access memory) and SMC (system management controller) resolves these conflicts.

Reset NVRAM (for Intel Macs)

Shut down your Mac completely. Turn it on and immediately hold Option + Command + P + R. Keep holding all four keys for about 20 seconds. Your Mac may restart during this time. Release the keys when you hear the startup sound a second time (on Macs that have startup sounds) or after 20 seconds have passed.

For Apple Silicon Macs (M1, M2, M3, M4 chips), NVRAM resets automatically when needed. No manual reset process exists.

Reset SMC (for Intel Macs)

The process varies by Mac model:

For MacBooks with removable batteries: Shut down the Mac, remove the battery, press and hold the power button for 5 seconds, reinstall the battery, turn on the Mac.

For newer MacBooks: Shut down the Mac, press and hold Shift + Control + Option on the left side of the keyboard, plus the power button, for 10 seconds. Release all keys simultaneously, then turn on the Mac normally.

For Mac desktops: Shut down the Mac, unplug the power cord, wait 15 seconds, plug the power cord back in, wait 5 seconds, then turn on the Mac.

Apple Silicon Macs don’t have SMC. The functionality is integrated into Apple’s chips and resets automatically.

Handle Encrypted Drives

Encrypted external drives require additional steps to mount. FileVault-encrypted volumes and third-party encryption both cause mounting complications.

If your drive is encrypted with FileVault (macOS’s built-in encryption), you should see a password prompt when connecting it. If this prompt doesn’t appear, the encryption metadata may be corrupted.

Open Terminal and run:

diskutil apfs list

Look for your drive in the output. If it shows as “Locked” or “Encrypted,” try unlocking it manually:

diskutil apfs unlockVolume /dev/disk2s1 -passphrase YourPasswordHere

Replace /dev/disk2s1 with your actual disk identifier and YourPasswordHere with your encryption password. If successful, the drive should mount.

For drives encrypted with third-party software like VeraCrypt, launch that specific application and mount the drive through its interface rather than through Finder.

Check for Hardware Failure

When software solutions fail, hardware problems become likely. Several diagnostic approaches help identify physical drive failures.

Listen to the Drive

Connect the drive and listen carefully:

Normal sounds: Gentle whirring or humming indicates the platters are spinning correctly. Occasional soft clicks during read/write operations are normal.

Warning sounds: Repeated clicking (the “click of death”), beeping, or grinding noises indicate mechanical failure. These sounds mean read/write heads are failing or platters are damaged. Continuing to power on a drive making these sounds can worsen data loss.

If you hear abnormal sounds and the data is critical, stop troubleshooting immediately. Power off the drive and consult a professional data recovery service like DriveSavers or Ontrack.

Test on Another Computer

Connect your external drive to a different Mac or even a Windows PC. If it mounts successfully elsewhere, the problem lies with your Mac’s hardware or software, not the drive itself. If it fails on multiple computers, the drive or its enclosure likely has hardware damage.

Check System Information

Go to Apple menu > About This Mac > More Info > System Report. In the left sidebar under Hardware, select USB (or Thunderbolt depending on your connection type).

Connect your external drive while System Information is open. If the drive appears in this list, your Mac physically detects it. The mounting problem is software-related. If nothing appears when you connect the drive, you likely have a bad cable, faulty port, or dead drive.

Try a Different Enclosure

Hard drive enclosures (the external case housing the actual drive) fail independently from the drive mechanism inside. If you’re comfortable with basic hardware work, external drive enclosures typically open with a few screws.

Purchase an inexpensive replacement enclosure compatible with your drive size (2.5″ or 3.5″) and interface (SATA, typically). Move your drive into the new enclosure and reconnect to your Mac. If it mounts successfully, the old enclosure was faulty.

Software Conflicts and Solutions

Third-party software occasionally prevents drives from mounting properly.

Boot in Safe Mode

Safe Mode loads only essential macOS components, bypassing third-party kernel extensions and login items that might interfere with mounting.

For Intel Macs: Shut down completely, then turn on while holding the Shift key. Release Shift when you see the login window.

For Apple Silicon Macs: Shut down, press and hold the power button until you see “Loading startup options,” select your startup disk, then press and hold Shift while clicking Continue in Safe Mode.

Once in Safe Mode, connect your external drive. If it mounts successfully, a third-party application or system extension is causing the conflict. Restart normally and systematically disable recent software additions until you identify the culprit.

Update macOS

Outdated operating system versions contain bugs that affect external drive mounting. Check for updates by going to Apple menu > System Settings > General > Software Update (on macOS Ventura or later) or System Preferences > Software Update (on earlier versions).

Install all available updates, restart your Mac, then test the drive again.

Remove Problematic Software

Security software, virtualization tools, and disk utilities sometimes conflict with macOS’s native drive management. Common culprits include:

• Older antivirus software
• VirtualBox or VMware Fusion
• Drive-specific utilities from manufacturers
• Cleaning utilities that modify system files

If you recently installed any software before the mounting problems began, uninstall it completely (don’t just drag it to the Trash; use the vendor’s uninstaller if provided) and restart.

Advanced Recovery Options

When standard repairs fail but the drive contains critical data, these advanced techniques might help.

Target Disk Mode

If you have access to another Mac, Target Disk Mode turns your Mac into an external drive enclosure. This bypasses potential issues with your Mac’s operating system.

Connect both Macs with a Thunderbolt or USB-C cable. Restart the Mac having mounting issues while holding the T key. It will enter Target Disk Mode, showing a Thunderbolt or USB symbol on screen. On the working Mac, both your problematic Mac’s internal drive AND any connected external drives should mount.

If your external drive mounts on the working Mac through Target Disk Mode, copy your data immediately. The problem lies somewhere in your Mac’s configuration, not the drive itself.

Recovery Mode Disk Utility

Recovery Mode loads a separate copy of macOS’s core utilities, which sometimes succeeds when the standard environment fails.

For Intel Macs: Restart and immediately hold Command + R.

For Apple Silicon Macs: Shut down, press and hold the power button until you see “Loading startup options,” then select Options > Continue.

Once in Recovery Mode, select Disk Utility from the utilities menu. Try mounting and repairing your external drive here. Recovery Mode’s Disk Utility sometimes has access to repair functions unavailable in the regular environment.

Data Recovery Software

If mounting attempts continue failing but you need to recover files, data recovery software can often extract data from unmountable drives.

Disk Drill offers a free version with limited recovery capabilities and a paid version with comprehensive features. It can scan unmountable drives and recover many file types even from corrupted file systems. Download from the Disk Drill official website.

PhotoRec is free, open-source recovery software that works exceptionally well for photos, videos, and documents. It ignores the file system entirely and searches for known file signatures. Learn more at CGSecurity’s PhotoRec page.

Both tools require some technical comfort but include detailed documentation. They’re worth trying before sending a drive to expensive professional recovery services.

Prevention: Avoiding Future Mounting Problems

Once you’ve resolved the immediate issue, these practices minimize future mounting failures.

Always Eject Properly

Never unplug an external drive without ejecting it first. In Finder, click the eject icon next to the drive name, or right-click the drive and select Eject. Wait until the drive disappears from Finder before disconnecting.

Unexpected disconnections corrupt file systems more than any other single cause. This five-second habit prevents hours of troubleshooting.

Use Quality Cables and Hubs

Cheap USB cables and unpowered hubs cause countless mounting problems. Invest in certified cables (look for MFi certification for Apple devices or USB-IF certification for USB-C). For hubs, choose powered models from reputable manufacturers.

Maintain Backups

External drives will eventually fail. Every hard drive has a limited lifespan. Maintain backups using the 3-2-1 rule: three copies of data, on two different media types, with one copy offsite. Use Time Machine for one backup and cloud storage or another external drive for the second.

Regular Disk Checks

Run First Aid on your external drives quarterly, even when they’re working fine. Proactive maintenance catches and fixes minor corruption before it prevents mounting.

Monitor Drive Health

SMART (Self-Monitoring, Analysis and Reporting Technology) data reveals drive health. Use DriveDx or SMART Utility to check your external drive’s SMART status periodically. These applications warn you about developing hardware problems before complete failure occurs.

When to Seek Professional Help

Recognize when DIY troubleshooting should stop. Seek professional assistance if:

• The drive makes unusual clicking, beeping, or grinding sounds
• You’ve dropped the drive or exposed it to water
• The drive has irreplaceable data (family photos, business records, etc.) and none of these methods work
• First Aid and fsck report physical damage to the disk
• You smell burning or see smoke/sparks from the drive

Professional data recovery services cost hundreds to thousands of dollars but can recover data from drives with severe physical damage. Companies like DriveSavers, Ontrack, and Gillware specialize in recovery and operate in clean room environments necessary for opening drive mechanisms.

Don’t continue powering on a drive with mechanical failure. Each attempt can make recovery harder and more expensive.

Conclusion

Most external hard drives that won’t mount on Mac have fixable causes. Start with simple solutions like checking cables and changing ports. Progress to Disk Utility’s First Aid, then terminal commands if needed. Address file system compatibility and reset system controllers when appropriate. Only after exhausting software solutions should you suspect hardware failure.

The specific path depends on your symptoms: drives that appear in Disk Utility but won’t mount usually have file system corruption fixable with First Aid or fsck. Drives that don’t appear anywhere often have hardware problems requiring cable replacement or professional intervention. Drives that mount on other computers but not yours indicate Mac-specific software conflicts.

Fix your mounting problem methodically, starting with the simplest solutions first. The most common issues resolve within 15 minutes. For stubborn cases, terminal commands and recovery mode attempt more aggressive repairs. When you hear mechanical failure sounds, stop immediately and consult professionals to avoid permanent data loss.