Summary: It's a definite guide to fix Mac not recognizing external hard drive without data loss, troubleshooting why the external hard drive is not recognized by macOS and how to access it in such situations. You can also download iBoysoft Mac Data Recovery to get files off when Mac doesn't recognize the external hard rive.
Whether you are using MacBook, MacBook Pro, MacBook Air, or iMac, it's inevitable the Mac can't recognize the external hard drive that you plug into.
Don't know how to make Mac recognize the external hard drive again? No worries.
Because after reading this post, you can:
- Learn how Mac accesses an external drive.
- Know why macOS doesn't recognize the external hard drive.
- Make external hard drive recognized by Mac again.
- Avoid data loss when the external hard drive is not working on Mac
According to different situations, this passage will show you solutions to fix 'Mac doesn't recognize external hard drive' issue accordingly.
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.
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 that your Mac has done so many works to recognize an external storage device while you just simply plug the external drive in.
However, if one or more steps above fail, the external hard drive would not be recognized and accessed successfully. In this case, we need a step-by-step check to troubleshoot why Mac doesn't recognize your external hard drive.
To make it more simple, we need to check these things:
- Is your external hard drive properly connected for data transferring and power supply?
- Is your Mac set to show up mounted external drives on the Finder and desktop?
- Does Mac read and recognize the partition information of this hard drive?
- Does Mac recognize the file system of the external hard drive successfully?
Now, let's check them one by one.
First of All, Check the Connections
Don't assume this is unnecessary. 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.
Usually, when the external hard drive is supplied with power, the light of a power-connected external hard drive is on and blinking. If not, try to check if the external hard drive needs to be externally plugged into the wall outlet. It happens most for some external desktop hard drives like WD Elements and Seagate Desktop devices that don't use USB port for power source.
2. Try another USB port to connect the external hard drive.
Portable hard drives like My Passport and iomega use USB port both for power and data supply. So, if the USB port is loose, damaged, lack of power, or dusty, the connected external hard drive won't be recognized by Mac.
3. Try to plug the external hard drive into the USB port slowly.
Strange though, some users notice that the external hard drive would be recognized and work well when they plug it in exceptionally slowly. It may because the USB port is out of shape and unstable. The tricks also work for other storage devices, including thumb drive, USB flash drive, etc.
4. Try another USB cable to connect the external hard drive.
In case the cable is broken, you can try another USB cable to connect the external hard drive to your Mac. And if it's an SD card that is not showing up on Mac, try another card reader. Don't worry if you don't have one right now, and you can skip and check other things first.
5. Try another USB hub or USB-C adapter.
Some MacBook after 2015 uses Thunderbolt 3 while some older ones use Thunderbolt 2, which could result in incompatibility. Thus, if the unrecognized external hard drive is a Type C drive, you can try to access it via another Mac. Instead, if it's a standard USB-A external hard drive and you connect it to Thunderbolt 3 port via USB-C adapter, you can try another USB hub or even another adapter, in case such adaption makes data transferring unstable.
6. Try to reboot your Mac.
Possibly, you improperly ejected the external hard drive the last time you use it on the Mac. As a result, Mac doesn't recognize the external hard drive this time because macOS thinks the USB port is taken by the unsafely ejected one.
Then Check if Mac is Set to Show up External Hard Drives
Usually, the external hard drive will be automatically mounted by Mac and then you can see it on 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, we need to check if the mounted external hard drive is allowed to show up.
Step 1: Go to Finder > Preferences >Sidebar.
Step 2:Select "External disks" under " Locations" to show your external hard drive in the Finder sidebar.
Step 3: Shift to General tab.
Step 4: Check "External disks" under "Show these items on the desktop" and your connected external hard drive will appear in Finder and on the desktop.
Third, Check if Mac Recognizes the Partitions of the External Hard Drive
Any storage devices, including HDD and SSD, need to be partitioned so that each section can be managed separately. And partition table or partition map records the necessary partition information of the external hard drive.
Mac won't read the external hard drive further once the partition table is damaged, lost, or corrupted. Fortunately, you can check this in Disk Utility.
Solution 1: Repair the external hard drive in Disk Utility
Disk Utility is a built-in disk repair tool on your Mac. It can manage, erase, check, and repair disk efficiently. It's free and powerful, so continue reading to know how to check this.
Step 1: Click Launchpad, find the Other folder and open it. Here, you can see and launch Disk Utility.
Step 2: Click "View" option at the upper left, and then choose "Show All Devices".
Step 3: If you can see volumes of the external hard drive in the left sidebar, be it lighted or greyed, select the name of unrecognized external hard drive.
Step 4: Click on the "First Aid" button in the top center and click "Run".
Tips: 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.
But if you can't see any partitions or volumes, or you run First Aid to repair the external hard drive but fail, then the partition information is not recognized by Mac. You need to move to the next solution in this situation.
Solution 2: Reformat the unrecognized external hard drive
If First Aid is unable to repair the unrecognized external hard drive, the disk might be corrupted too seriously to be repaired. Under this circumstance, the only solution is to erase this external hard drive in Disk Utility and assign new partition schemes.
Warning: Reformatting will wipe your data off the unrecognizable external hard drive. So, before you follow the steps below, make sure you have a copy of backups. If you don't have any backup in hand, you can also recover data from the unrecognized external hard drive with iBoysoft Mac Data Recovery.
Step 1: Launch Disk Utility.
Step 2: Select the unrecognized external hard drive on the left.
Step 3: Click the "Erase" at the top of the Disk Utility window.
Step 4: Complete the related information (name, format, scheme), then click "Erase".
Tips: Click here to learn the differences between GUID, Master Boot Record, Apple Partition Map if you don't know to choose which partition scheme in Disk Utility.
How to Prevent Data Loss When Mac Doesn't Recognize External Hard Drives?
When the external hard drive is not working normally, the first concern for most users is the important data on the drive. However, if you have tried possible solutions but Mac just doesn't recognize the external hard drive still, how can you access your data?
The good news is, you can recover data from this unrecognizable external hard drive with free Mac data recovery software like iBoysoft Mac Data Recovery.
iBoysoft Mac Data Recovery is one of the best hard drive data recovery software. It can recover data from the external hard drives when it's not recognized, not readable, not working or not showing up on Mac. Moreover, this data recovery software can recover data from formatted, corrupted, and unmounted external hard drives. It supports data recovery from APFS, HFS, HFS+, exFAT, FAT32 formatted hard drives.
This program works with macOS 10.15 (Catalina), macOS 10.14 (Mojave), macOS 10.13 (High Sierra), macOS 10.12 (Sierra) and OS X 10.11 (El Capitan), 10.10 (Yosemite), 10.9 (Mavericks), 10.8 (Mountain Lion), 10.7 (Lion).
Step 1: Install and launch iBoysoft Mac Data Recovery on Mac.
After downloading and launching this Mac data recovery software, you can connect the unrecognized external hard drive to your Mac. Later, it will be detected and show up in this software.
Step 2: Select the unrecognized external hard drive to scan for lost data.
Find the unrecognized external hard drive in the list, click on it, and then choose "Scan" to search for data on this hard drive.
Step 3: Preview the searching results and recover the target ones.
As we mentioned before, you can't access and view your important data on the unrecognized external hard drive. But with the assistance of iBoysoft Mac Data Recovery, you get a chance to check the condition of your data by using its Preview feature. Simply filter the scanning result, select the data to preview, and click "Recover" to get them back.
Last, Check if Mac Has Recognized the File System of the External HDD
The file system manages how your data is stored on the external hard drive. If your partition map seems to be OK, the next thing we need to confirm is that if Mac has recognized the file system of each partition.
So, just go to Finder > Go > Utilities > Disk Utility and check if you can see the partitions of the external hard drive there and fix the Mac not recognizing external hard drive issue with the following solutions.
Solution 1: Manually mount the external hard drive if it's greyed out in Disk Utility
Chances are that Mac has recognized the external hard drive, but for some reason, Mac fails to automatically mount it. So, if you can see the volumes of the external hard drive with correct disk information (name, file system, storage capacity, etc.), try to force mount the external hard drive in Disk Utility.
Step 1: Open Disk Utility.
Step 2: Click "View" option at the upper left, and then choose "Show All Devices".
Step 3: Right-click on the volume that you want to access, not the external hard drive this time.
Step 4: Choose "Mount" in the context menu.
If nothing happens or macOS reports some errors, keep reading and repair the unrecognized external hard drive with First Aid.
Solution 2: Repair the external hard drive with First Aid if you can't mount it
If you can't mount the external hard drive in Disk Utility, the drive might have some file system corruptions. But don't be panic when you hear "corruption", you still have solutions when Mac can’t recognize the external hard drive’s file system.
Step 1: Launch Disk Utility as you did before.
Step 2: Click "View" option at the upper left, and then choose "Show All Devices" in the context menu.
Step 3: Select the corrupted volume in the list, not the name of the external hard drive.
Step 4: Click on the "First Aid" button in the top center and then click "Run".
If you run First Aid successfully, go to check if the external hard drive is recognized by Mac. If it fails, you need to expand the "Show Details" option to see more information. Also, if you received an error like "file system check exit code is 8", "invalid b tree node size", or other messages, the file system of the external hard drive might be seriously corrupted and can't be repaired.
Read further and check what you can do.
Solution 3: Recover data and reformat the corrupted external hard drive
What if First Aid fails to repair the corrupted file system? Well, in this case, we strongly recommend you to recover your important data from the unrecognized external hard drive if you don't have backups, and then you can fix Mac not recognizing external hard drive by reformatting.
Step 2: Launch Disk Utility and select the unrecognized partitions of the external hard drive.
Step 3: Click the "Erase" at the top.
Step 4: Fill in the name and format you want to use, and then click Erase to reformat.
After these operations, your external hard drive should be recognized by Mac again. But if the external hard drive is not showing up in Disk Utility, unfortunately, your external hard drive has hardware problems. You could either contact the support team of the hard drive manufacturer for product repair and replacement, or you can send the unrecognizable external hard drive to a local disk repair service for help.
As you can see, Mac needs to do a lot of work to recognize an external hard drive. If any step fails, the external hard drive is not recognized by Mac. Don't be panic and these solutions above will help you beyond this issue.
When you access your external hard drive through Mac, Windows, or other types of computer, remember:
- Do not eject the external hard drive when it is transferring data.
- Always safely eject the external drives when you remove it from the Mac.
- Take good care of the external hard drive and keep it away from unfavorable environmental.
Let us know if this guide helps when your Mac doesn't recognize the external hard drive!