How to fix external hard drive not mounting on Mac issue without data loss?

By Juno | Posted to Mac Data Recovery Tips, updated on August 12th, 2020 |

Summary: External hard drive not mounting on Mac means that you can't access data stored on it. This page helps you mount external hard drives, as well as SD cards and USB flash drives, etc. on Mac. If the external hard drive won't mount on Mac, you can download iBoysoft Data Recovery for Mac to recover lost data from unmountable external hard drives.

Usually, an external hard drive will be mounted automatically on your Mac once you plug it in, and you can access data on this drive. So, it's annoying when you find that your external hard drive is not mounting or recognized by your Mac, just like the user below.

"I have a 500 GB older HP external hard drive, formatted as macOS Extend journaled on MacBook Pro 2014 and I have been using it to do Time Machine backups. Now after updating to macOS Mojave, this external hard drive just won't mount. The main drive shows in Disk Utility but the backup partition is not showing up. I can't do First Aid as it doesn't show up. Any ideas? Thanks! I need help to recover my important files from this unmountable external hard drive."

This post will tell you why your external hard drives won't mount on your Mac, as well as teach you how to fix this disk problem without losing data.

Table of contents
1. Dos and don'ts of external hard drive not mounting problem
2. How to fix external hard drive not mounting on Mac issue without data loss?
3. Why an external hard drive won't mount on Mac?
4. Knowledge Base: what does it mean to mount a hard drive on Mac?

Dos and don'ts of external hard drive not mounting problem

Before you go further, it's better to know what you can do and can't do if an external hard drive is not mounting on Mac.

When your disk become unmountable on Mac, you should not go straight to reformat this external hard drive, especially when you have important files on it. This is because reformatting will wipe the data on this drive and cause serious data loss if you don't have a copy of a data backup.

On the contrary, you should stop using this external hard drive right away. The reason for such cautiousness is that any further operation is very likely to overwrite your original files and make them unrecoverable.

Key takeaway:

  • Do not erase this external hard drive before you get your data back.
  • Do not save new things to this drive, or perform other operations like deletion, file removal, etc.

Now, let's go into fixing the external hard drives not mounting on Mac issue.

Fix external hard drive not mounting on Mac issue without data loss

How to fix external hard drives not mounting on Mac issue without data loss?

To help your external hard drive mount on Mac, try solutions suggested in this part one by one. Hopefully, you'll be able to mount this external hard drive on Mac again without data loss.

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

In case you miss anything necessary, you can first have some basic checks as following when your external hard drive is not mounting on your Mac computer.

1. Re-plug your external hard drive to another port or try another USB cable. A faulty connection, though it is foolproof, is often the key to fix the external hard drive not mounting issue, in that users always forget to check if the port is wobbly or if the cable is broken.

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 hard drive normally, the Mac doesn't recognize the disk.

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

show mounted external hard drive on Mac desktop

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

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

If your external hard drive is not mounted on the desktop or in the Finder, you can try to mount it manually in Disk Utility (a native disk management tool in your Mac).

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

1. Click Go at the upper left of your desktop and go to Utilities, then launch Disk Utility on your Mac computer.

2. Click on "Show All Devices" in View option to list or connected drives.

3. Choose the unmounted external hard drive in the left sidebar.

3. 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), it is very likely that your disk is 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 the external hard drive on Mac. First Aid is a very simple tool that is built in your Mac, and it is able to 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.

Follow the instructions and repair the external hard drive that is not mounting.

1. Go to Utilities and launch 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.

Repair this unmountable external hard drive with First Aid

Solution 3:Fix the external hard drive not mounting issue by reformatting

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

Disk Utility failed to repair the not mounting external hard drive

Disk Utility can't repair this disk, what do to?

In this case, you need to back up your important data on the external hard drive, such as family photos, valuable work documents, or any other files. If you don't have a copy of a data backup in hand, the following guide can help you recover lost data from this unmountable external hard drive. And then, you can reformat your exteranl hard drive and mount it on Mac.

How to recover lost data from unmountable external hard drives on Mac?

As long as your external hard drive doesn't have any hardware problem, fortunately, you can retrieve your files with professional Mac data recovery software - iBoysoft Data Recovery for Mac with no fuss.

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

  • Recover lost data from unmountable, formatted, inaccessible, unreadable, corrupted external hard drives.
  • Supported storage devices: external hard drives, USB flash drives, memory cards, SD cards, etc.
  • Supported file types: photos, videos, audio files, documents, emails, etc.
  • Suppported Mac OS: macOS 10.15/1.14/10.13/10.12 and Mac OS X 10.11/10.10/10.9/10.8/10.7.

Read-only & risk-free

Tutorial for external hard drive data recovery on Mac with iBoysoft Data Recovery for Mac

1. Free download and install iBoysoft Data Recovery for Mac on Mac.

2. Launch iBoysoft Data Recovery for Mac.

Recover lost data from not mounting external hard drive on Mac with iBoysoft Data Recovery for Mac

3. Select the external hard drive that is not mounting and click Scan button to scan for all lost data.

4. Preview the searching results, choose files you need, and click Recover to get them back.

Preview and Recover lost data from not mounting external hard drive on Mac with iBoysoft Data Recovery for Mac

Note: You need to save the recovered files to another usable drive. By this means, you will not lose them again when you move forward to the steps to fix not mounted external hard drives in the following part.

5. Have a check to ensure you have got all lost data back.

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

Tutorial to reformat unmountable external hard drives on Mac

1. Launch 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 (name, format, scheme), then click Erase button to finish reformatting.

Erase disk to fix unmountable external hard drive on Mac

After reformatting, your external hard drive will be assigned with a new file system. And you can go ahead to mount this drive on your Mac normally.

Then, why an external hard drive is not mounting on Mac?

You probably don't know why this external hard drive is not mounting on Mac. As a matter of fact, this problem could be caused by many factors, such as damaged file system, virus attack, unsafe ejection or any other improper operations.

Here are some common ones.

  1. A damaged file system: If your external hard drive is attacked by virus or if you abruptly eject this drive, it's likely that the file system of this disk would be damaged or corrupted. As a result, the operating system is unable to recognize this disk, and the disk will not be mounted or read by macOS.
  2. Connection problems: Another reason that your external hard drives is not mounting 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 drive has too much bad sectors or have been physically damaged.

Knowledge Base: what does it mean to mount a hard drive on Mac?

Mounting a hard drive means the operating system reads information about the file system from the disk's partition table, and then gives the hard drive a mount point. So, mounting is a necessary step before the operating system can access a disk (including read from and write to).

Therefore, if an externalhard 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.

Conclusion:

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 for Mac to recover your files first. Remember that, no matter what disk problem you meet, you should perform hard drive data recovery before reformatting the problematic drive.