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External Hard Drive Not Mounting Mac? Fix It without Data Loss

Updated on Monday, July 15, 2024

iBoysoft author Sherry Song

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Sherry Song
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Jessica Shee

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Summary: This page helps solve the external hard drive not mounting on Mac issue. You can download iBoysoft Data Recovery for Mac to retrieve data from this external hard drive.

external drives is not mounting on Mac

Usually, an external hard drive will mount automatically once you plug it into the Mac's port. And then you can find and access the external hard drive on your Mac. So, it's annoying when you find that your Mac external hard drive not mounting for the com.apple.DiskManagement.disenter error or not recognized by your Mac, just like the user below.

"I have a 500 GB LaCie external drive, formatted as macOS Extend journaled on MacBook Pro 2014 and I have been using it to do Time Machine backups. Now after updating, macOS is not mounting this external drive. The main drive is greyed out in Disk Utility and the partition is not showing up. I can't do First Aid as my LaCie external drive does not mount on the MacBook Pro. Any ideas? Thanks!"

Wondering "why my external hard drive won't mount on Mac"? This post explains the reasons and teaches how to fix this disk problem without losing data.

Quick takeaways for external hard drive not mounting on Mac:

SolutionEffectivenessDifficulty level
Check connectionsLow if the connection is not the problem. High if connection causes the issue.Easy
Check settingsSimilar to checking connectionsEasy
Force MountHard to say - it depends on whether the disk is damaged or notMedium
First AidHard to say - It depends on how badly the disk is damagedMedium
ReformattingHigh if you follow the tutorial step-by-stepHard
Third-party disk mounterHigh if the file system of the disk is the problemEasy

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There is a video tutorial you can follow to fix an external hard drive not mounting/showing up on Mac.

Recover data from an external hard drive that won't mount

Couldn't mount my external disk. Restarted, tried (even) my Catalina partition and nothing. 

Downloaded iBoysoft just to try to double check if any essentials are on there. 

Then after 5 hours it's mounted. HOW? Is it on it's last legs?

— Steve Curtis (@stevenpcurtis) November 24, 2020

Best External Hard Drive Data Recovery - iBoysoft Data Recovery for Mac

  • Recover lost data from unmountable storage devices: external hard drives, USB flash drives, memory cards, sd cards, etc.
  • Supported recovering photos, videos, audio files, documents, emails, etc from the disk that's not mounting on Mac.
  • Supported Mac OS: macOS 14/1312/11/10.15/10.14/10.13/10.12 and Mac OS X 10.11.

 Read-only & risk-free


Tutorial for external hard drive data recovery on Mac

  1. Free download and install iBoysoft Data Recovery for Mac on your Mac computer.
  2. Launch iBoysoft Data Recovery for Mac.
  3. Select the external drive that is not mounting and click the Search for Lost Data button to scan for all lost data.
    scan external disk
  4. Preview the searching results once the scanning process is completed, choose the files you need, and click Recover to get them back.
    preview files
  5. Have a check to ensure you have got all lost data back on the not mounted external disk.

 Note: You need to save the recovered files to another usable drive.

After having successfully restored all data on this drive, you can set out to erase this external drive to fix the external hard drive not mounting on Mac issue.

If these steps are helpful, why not share them with others?


Dos and Don'ts When External Hard Drive Not Mounting on Mac

Before you go further, it's better to know what you can do and can't do.

 1. Do not go straight to reformat this not-mounted external drive unless you've restored data from it or backed up it before. Reformatting will wipe the data on this disk and cause serious data loss.

 2. Do not run First Aid to directly repair the disk if you didn't restore data from it or back up it. Any further operation is very likely to overwrite your original files and make them unrecoverable.

 3. Check if you have a copy of a data backup. If not, recover important files from this unmountable external drive first to avoid data loss.

Now, let's troubleshoot the issue and mount an external Mac hard drive.

Fix external hard drive not mounting on Mac

To mount an external hard drive that is not mounting on Mac, try the solutions suggested in this part one by one. Hopefully, you'll be able to open this external drive on Mac again.

First, try some simple tricks to mount an external hard drive on Mac

In case you miss anything necessary, you can first have some basic checks as follows:

 1. Re-plug your external hard drive to another USB port or try another USB cable.

A faulty connection, though it is foolproof, might be the key fix if the LaCie thunderbolt drive is not mounting, in that users always forget to check if the Mac's USB port is wobbly or if the USB cable is broken. If you are using a USB connector or adaptor, change another one to connect the drive with your Mac.

 2. Try a super slow jam.

Strange but true, some users found that their external will mount properly when they plug it in exceptional slow motion. However, if they try and plug in the external drive normally, the Mac doesn't recognize the disk.

 3. Check your Finder Preferences.

When your external hard drive does not appear on the desktop, you can open Finder, choose "Preference" (or press Command +, ) and check "External disks" both in the General tab and in the Sidebar tab to show your external hard drive on your Mac computer.

show mounted external hard drive on Mac desktop

If Mac could not mount the external hard drive on the desktop still, let's troubleshoot this issue with the following solutions.

Solution 1: Force mount this external hard drive in Disk Utility

If you can't find the external drive on the desktop or in the Finder, Disk Utility is the last place where you can find the external disks. Some Mac users reported that external hard drive shows up in disk utility but won't mount, then you can force mount disk on Mac.

Here is how to mount an external hard drive on Mac:

  1. Find Disk Utility by clicking Go at the upper left of your desktop and go to Utilities, then open Disk Utility on your Mac computer.
  2. Click on the "Show All Devices" in the Disk Utility's View menu to show external hard drive icon.
  3. Choose the grayed external drive in the Disk Utility's sidebar.
  4. Select Mount in the top center of Disk Utility.

However, if you find that your external hard drive is not showing up in Disk Utility (not a single volume but the whole disk disappears), your disk is likely suffering some physical damage. In this case, you need to send it to a local data recovery service. But if the Mount option is grayed out and you can see this external hard drive in Disk Utility, you can try another solution then.

Solution 2: Repair this unmountable external hard drive with First Aid

The second suggestion is First Aid in Disk Utility if you are unable to mount Mac external hard drive. It is a very simple tool that is built into your Mac, and it can detect and repair directory damage and other disk errors. You are advised to run the tool more than once to ensure you are receiving a consistent result.

Note that you should recover data from the unmountable external drive without a backup before running First Aid.

Follow the instructions and repair the Mac external hard drive not mounting.

  1. Go to Utilities and open Disk Utility on your Mac computer.
  2. Select the unmountable external hard drive on the left sidebar.
  3. Select First Aid in the top center and click Run.

Solution 3: Reformat the unmounted external hard drive

If your external hard drive still can't be mounted in Disk Utility after you perform First Aid, or if Disk Utility can't repair this disk, your drive should have some serious errors like file system corruption.

Disk Utility failed to repair the not mounting external hard drive

In this case, you need to back up your important data on the external drive, such as family photos, valuable work documents, or any other files given that erasing the drive will delete all the data. If you don't have a copy of a data backup in hand, the above guide can help you recover data from this unmountable external hard drive. And then, you can reformat it to fix external hard drive is not mounting on Mac.

Tutorial to reformat unmountable external hard drives on Mac

1. Open Disk Utility.
2. Click the icon of your unmountable external hard drive on the left sidebar.
3. Click on the Erase button function on the top of the Disk Utility window. 
Repair this unmountable external hard drive with by reformatting  
4. Complete the related information, including name, format(APFS/Mac OS Extended, and scheme, then click Erase button to finish reformatting. 
Erase disk to fix unmountable external hard drive on Mac

After reformatting, your external drive will be assigned with a new file system so that you can mount this unmountable hard drive again. 

Solution 4: Use a third-party external drive mounter

When you format the drive with an macOS unsupported file system on a Windows PC, you will fail to mount it on Mac. If you find your NTFS drive won't mount on macOS 10.15.7 after the Apple security update on March 17, 2022, and the "com.apple.DiskManagement.disenter error 49221" issue occurs when you're trying to mount it with Disk Utility, then, the solution is a little different from the above. Instead, you should use professional NTFS software to fix it.

iBoysoft NTFS for Mac is a professional NTFS for Mac software that supports macOS 14/13/12/11/10.15/10.14/10.13. It can mount NTFS formatted external hard drives, USB flash drives, etc. with full access. Here's how to use it to fix the NTFS drive not mounting on macOS Catalina 10.15.7 after the security update.

  1. Free download, install and launch iBoysoft NTFS for Mac on your computer.
  2. Connect your Windows NTFS external hard disk to your Mac. Then, your NTFS drive will be mounted automatically. You'll now be able to open your NTFS drive and write to it. 
    iBoysoft NTFS for Mac menu bar

Why can't mount the external hard drive on Mac?

Probably, the user above would never know why his MacBook is not mounting the external hard drive. As a matter of fact, this problem could be caused by many factors, such as damaged file systems, virus attacks, unsafe ejection, or any other improper operations.

Here are some common ones.

1. A damaged file system: If your external drive is attacked by the virus or if you abruptly eject this drive, the file system of this disk would likely be damaged or corrupted. As a result, the operating system not recognizing external hard drive with disk errors, and the disk will not be mounted or read by macOS.

2. Connection problems: Another reason that the hard drive won't mount on Mac could be a dirty or loose connection between your cable, USB-C multi-adapter, Thunderbolt 3,  or other connecting ports. A clear, clean, snug, and fit tightly connection is the premise of mounting an external hard drive successfully.

3. Hardware issue: Also, problems related to hardware could also make the disk unmountable, especially when your external hard disk has too many bad sectors or has been physically damaged.

Knowledge Base: What does 'Mount' mean on Mac?

Mounting an external hard disk means the macOS gives a mount point (entrance) to read and access information on the hard drive. Information is accessed by the disk file system and partition table. So, it's a necessary step before the operating system can access a disk (including read from and write to).

Therefore, if an external hard drive won't mount on Mac, it means the system gets into trouble in recognizing the file system or other information of this hard drive.

Let's share this helpful tutorial and wonderful software to help more people!



If your external hard drive is not mounting on your Mac, don't panic. Most of the time, you are going to fix this disk problem with the solutions above. Moreover, if you worry about data loss when the disk becomes unmountable, you can use iBoysoft Data Recovery to recover your files first. Remember that, no matter what disk problem you meet, you should perform data recovery in case of losing data.

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