Fix Mac Doesn't Recognize External Hard Drive (New for macOS 12)

By Katrina | Posted to Home > Mac Data Recovery Tips, updated on November 16th, 2021

Summary: This post will let you find the reasons why Mac doesn't recognize your external hard drive and how to fix it. And you can learn how to detect drive and retrieve data with iBoysoft Data Recovery for Mac.

How to fix Mac not recognize external hard drive

Whether you are using MacBook, MacBook Pro, MacBook Air, or iMac, strangely, sometimes the Mac can't recognize the external hard drive that you plug into. Recently this issue affects some Mac models after updating to macOS 12 Monterey as well.

How to make Mac detect the external hard drive again? We offer a detailed guide in this post to fix the Mac not recognizing the external hard drive issue. You will find it helpful for the seem-to-be-dead USB ports on Macs running macOS Monterey.

And after reading this post, you can:

  1. Learn how Mac accesses an external drive.
  2. Know why macOS doesn't recognize the external hard drive.
  3. Make external hard drive recognized by Mac again.
  4. Get data back when the external hard drive is not working on Mac
external hard drive

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Overview of macOS recognizing an external hard drive

When your Seagate, WD my passport, Toshiba, or other external hard drive is not recognized by Mac, the first thing is to know which part of the recognition process goes wrong.

External hard drive for MacBook

So let's take a closer look at how macOS recognizes an external hard drive.

Step 1: The external hard drive is connected to your Mac.

Plugging the external hard drive into a computer will establish the hardware connection, which would supply the external hard drive with power source and data transferring capability. Visually, you can see the external hard drive lighting on and hear it spinning.

Step 2: macOS detects the external hard drive.

After the connection, the Mac would detect that a new storage device is plugged in. It's going to tell the device's type and manufacturer information, which will help macOS know how to load and read this external hard drive.

Step 3: macOS reads the external hard drive.

After recognizing the hardware information of the external hard drive, the Mac will call other system components to read the external hard drive’s type and partition information. If the hard drive is readable by the Mac, a visible disk icon would be formed consequently.

Step 4: macOS recognizes the files in the external hard drive.

Once Mac successfully reads the partition information of the external hard drive, it will go further by calling related programs to recognize the file system of each partition on the external hard drive. A recognized file system will let macOS know how and where your data is stored on the external hard drive, so that it can mount this external hard drive for use.

Step 5: Mac shows the external hard drive for users.

Going so far, macOS has recognized the external hard drive. Meanwhile, other programs get notified that there is a new volume available. But to make it convenient for users to access the data on the drive, it will check the system preferences and decide if users want to automatically mount and show the external hard drive on the desktop and in the finder.

Amazing, right? You probably never know the details. Your Mac has done so many works to recognize an external storage device, while you just simply plug the external drive into the USB port.

However, if one or more steps above fail, the external hard drive would not be recognized by Mac successfully. You can't access it. Namely, we need to check these things:

  1. Is your external hard drive properly connected for data transferring and power supply?
  2. Is your Mac set to show up mounted external drives on the Finder and desktop?
  3. Is the macOS 12 bug causing your Mac not to recognize the external hard drive?
  4. Does Mac read and recognize the partition information of this hard drive?
  5. Does Mac recognize the file system of the external hard drive successfully?

Now, let's check them one by one.

Mac not recognizing external hard drive: Check the connections

First things first. It turns out that most of the time, Mac doesn't recognize external hard drives, USB flash drives, pen drives, SD cards, etc. just because the drive is not properly connected.

Since a good connection is a basic condition for secondary hard drives working on the Mac, we need to try these things step by step.

  1. Make sure the external hard drive is supplied with power.
  2. Try to re-plug the external hard drive.
  3. Try another USB port to connect the external hard drive.
  4. Try to plug the external hard drive into the USB port slowly.
  5. Try another USB cable to connect the external hard drive.
  6. Try another USB hub or USB-C adapter.
  7. Try to reboot your Mac.

After trying all the methods to enable your MacBook or Mac to connect the external hard drive successfully, your Mac doesn't detect the external hard drive yet? Maybe your Mac is set not to display the external hard drives.

Mac doesn't recognize external hard drive: Check Finder settings

Usually, the external hard drive will be automatically mounted by Mac. Then you can see it on the desktop or in Finder in seconds. But this time, the external hard drive is not showing up on your Mac. Does this mean the external hard drive is not recognized by Mac? Probably not. On the contrary, you need to check if the mounted external hard drive is allowed to show up.

  • 1. Go to Finder > Preferences > Sidebar.
  • 2. Select External disks under Locations to list your external hard drive in the Finder sidebar.
  • show external hard drive in Finder
  • 3. Shift to the General tab.
  • 4. Check External disks under "Show these items on the desktop". Then your connected external hard drive will appear in Finder and on the desktop.

show external hard drive on the desktop

Chances are that you can’t see the external hard drive still. Go ahead to check if this issue is really caused by the macOS 12 bug.

Is macOS 12 bug causing Mac not to detect the external hard drive?

It’s easy to check if macOS 12 bug causes Mac not to recognize the external hard drive. Just try your external hard drive on another healthy Mac installed with any other macOS except for macOS 12.

macOS Monterey

If the connection and the Finder settings are good and another Mac successfully recognizes the external hard drive, then the Mac not recognizing external hard drive problem is caused by the macOS bug indeed.

To fix it, you can downgrade your macOS or reinstall macOS to avoid the macOS 12 bug. Otherwise, you can contact the developer on Apple’s support page to ask for a driver update since maybe it is the original 32-bit driver that makes your external drives not working.

But if your external hard drive can't be detected by another Mac, either. It means it's not the Mac device's fault. Then you should check if the hard drive itself has some problems and causes Mac not to find the external hard drive.

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Mac not detect external hard drive: Check it in System Information

The System Information app provides detailed specifications and other information about your Mac. In some versions of OS X, this app is called System Profiler. So, if the connections are good, you can check whether the connected external hard drive is detected in System Information or not.

  • 1. Choose the Apple menu > About This Mac.
  • 2. Click the System Report button to see more details provided by the System Information.
  • 3. Find and click the USB option under the Hardware section.
  • Check if Mac recoginzed the external hard drive in System Information
  • 4. Check if the external hard drive is recognized here or not.

If you can find the USB external hard drive in System Information, it means macOS has detected this drive. But why can't access the external hard drive on Mac still? Probably it’s time to check if there are partition table or file system issues on your external hard drive for Mac.

Mac not recognize external hard drive: Check its partitions

A partition table or partition map records the necessary partition information of the external hard drive. If the partition table is damaged, lost, or corrupted, Mac won't read the external hard drive further.

Fortunately, you can easily check this by downloading and launching our data recovery software - iBoysoft Mac Data Recovery. Just do the following to have a check:

Step 1: Install and launch iBoysoft Data Recovery for Mac on your MacBook.

Step 2: Connect the unrecognized external hard drive to your Mac.

Step 3: Wait a few seconds, check if the drive is detected, and show up in this software.

Recover lost data from not recognized external hard drive on Mac

If you can’t see your external disk in our app, it seems the partition table of your external hard drive is extremely corrupted or there are hardware problems on it. You should send the unrecognizable external hard drive to the manufacturer or a local disk repair service for help.

However, if you can find your unrecognized external disk appearing in our program, lucky for you, it means the partition table of your external drive is only slightly damaged and easy to fix by First Aid in Disk Utility.

Here’s how to run First Aid in Disk Utility to fix a corrupted or damaged external hard drive and make it detected again by Mac:

  • 1. Click Launchpad, find the Other folder, and open it. Here, you can see and launch Disk Utility.
  • 2. Click the View option at the upper left, and then choose "Show All Devices".
  • 3. If you can see volumes of the external hard drive in the left sidebar, be it lighted or greyed, select the name of the unrecognized external hard drive.
  • 4. Click on the First Aid button in the top center and click Run.
  • Repair the unrecognized external hard drive in Disk Utility

If you failed to repair the external hard drive by running First Aid, then the disk might be corrupted too seriously. You need to format the external hard drive on Mac and assign new partition schemes.

Please be noted that reformatting will wipe your data off the unrecognizable external hard drive. So, make sure you have a copy of backups before reformatting. If you don't have any backup in hand, you can also recover files from the external hard drive on Mac with the iBoysoft Data Recovery for Mac app.

preview lost data on the unrecognizable external hard drive on Mac

Mac doesn't recognize external hard drive: Check its file system

If your partition map seems to be OK now, however, you still can’t find the external hard drive on Mac or MacBook. Perhaps it’s the file system issues that cause the external hard disk not to be detected in macOS.

Let’s check it further. Open Disk Utility, you can see if the file system is Windows NTFS in the right column. If so, you can't mount the external hard drive in Disk Utility and can’t access files on it. To solve this issue, use an NTFS for Mac software or reformat it as FAT32, exFAT, or APFS.

If it is not NTFS but any other macOS-friendly file system, it’s possibly because the external hard drive has been encrypted. If it's a WD external hard drive that is not recognized by Mac, you can check if it is encrypted by WD Security. If so, simply unlock it with WD Discovery and access the external hard drive again.

Mac not recognizing external hard drive FAQs

1. How to access external hard drives on Mac?

Connect the external hard drive to your Mac via the USB port. After macOS detects the external hard drive successfully and shows the device's type and manufacturer information, access the files on the external hard drive in Finder after they're showing up.

2. What do I do if my external hard drive is not detected?

  1. 1. Make sure the external hard drive is supplied with power.
  2. 2. Try to re-plug the external hard drive if Mac doesn't detect this external hard drive.
  3. 3. Try another USB port to connect the external hard drive.
  4. 4. Try to plug the external hard drive into the USB port slowly.
  5. 5. Try another USB cable to connect the external hard drive.
  6. 6. Try another USB hub or USB-C adapter.

3. How do I force my Mac to mount an external hard drive?

First, make sure that your external hard drive is correctly connected to your Mac computer. Next, reboot the Mac computer and open Disk Utility, locate and select the unmounted drive. Finally, select Mount at the top menu.