We believe every one of you has encountered this situation. When you insert an external hard drive, let’s say, a USB disk drive, but you can’t see it on your computer. It seems like your computer doesn’t recognize it. Though annoying and frustrating it may be, you have plenty of solutions to fix this issue. Check the guide below.

Process of Mac recognizing an external hard drive

Before you dive into anything deeper, have you ever wondered how Mac deals with the external disks? When you plug a USB hard disk into the computer, the computer actually does many things within seconds.

When you plug the disk into your computer, the computer senses there’s an external device through the hardware connection and quickly starts to read the information on the device. The macOS reads the recognition information of the disk itself, partitions and file systems. After the macOS recognizes the disk, its partitions and file systems, the macOS will mount the external HD via a compatible disk driver. After the external hard drive is successfully mounted, the icon of the drive will be display on desktop, in Finder and in Disk Utility for your easy access to the files and the disk itself. Then you can read and write to the disk freely.

As you can see, it’s a delicate process. If any step goes wrong, the external HD can’t be used on the Mac normally

How to fix Mac not recognizing the external hard drive?

There are actually two situations for this problem. One is the computer does not detect or recognize the external HD. The other is the macOS recognizes it, but the disk doesn’t show up. Even though the two situations will result in people like you believing the external hard drive unrecognized, they are different and different solutions will be illustrated below.

Situation one: Mac does not detect the external HD 

For this situation, the problem mainly lies in the connection. How to make sure the connection is built?

1. Remember to charge your disks if necessary

For most external HD, they use the USB port as the power source. However, some desktop hard drives require an external on-the-wall outlet charge. So, make sure your device is supplied with power so that it can be recognized by the Mac.

2. Change another USB port, cable, or hub

All the broken, loose, or worn-out hardware can be responsible for Mac not recognizing external HD. Therefore, if there’s invalid recognition, you can change the USB port, cable, adapter or (and) the hub.

3. Reboot your Mac

If you ejected your disk in an improper way last time, the Mac would think the USB port is still occupied by the disk. As a result, it’s possible the Mac won’t recognize the disk when you plug it next time. By rebooting your Mac, the computer wipes out the information and gets connected with your disk through the USB port again.

If the connection is well-built, your Mac is supposed to detect the external hard disk. If the HD still doesn’t appear for your access, the disk is probably physically broken and needs to be replaced.

However, it happens a lot that Mac does detect the external HD but doesn’t show up. For this situation, we have the following methods.

Mac does detect the external HD but doesn‘t show up 

1. Change Finder’s Preferences

Generally speaking, the computer will automatically show the external disks. However, sometimes the computer is set to hide them. How to change the settings to make it shown? There are two ways.

• Go to Finder on the upper left of the desktop > Preferences > General tab and select “External disks”. Then you can see the external storage device on the desktop.

• To see your external HD in the Finder, you can go to Finder on the upper left of the desktop > Preferences > Sidebar and make sure the “External disks” under “Locations” is ticked. Then your external hard drive will appear in Finder.

2. Repair the removable hard disk

To repair a corrupted disk, first, you launch Disk Utility and click View option at the upper left. Then, choose “Show All Devices” in the context menu. Next, you can either right-click the name of the external hard drive, or the corrupted volume in the list. Last, click on the First Aid and then click Run. We suggest you use First Aid for several times to get consistent results. By doing so, the disk is supposed to be repaired.

3. Format your externa HD

If your external HD is too seriously damaged to be repaired by First Aid, or your Mac is not compatible with the file system of the disk, formatting your external disk is a good choice. Here’s what you should do.

Restore lost data from this unrecognized external hard drive with Mac data recovery software first because formatting will erase all stored data. We’ve used the software many times and it works pretty well. Next, open Disk Utility and right-click the unrecognized external hard drive. Then, choose Erase in the context. Last, fill in the name and choose format you want to use, and then click Erase to format.

4. Change another computer

For the incompatibility between the computer and the file system, there is actually a much easier way to fix this issue. That is to move to another computer. For example, if the external hard disk is using NTFS, apparently you are unbale to write to it on your Mac. In this case, you can just insert the disk on a Windows operating system and it’s supposed to work.

Apart from the above reasons and methods, you can also make your external HD recognizable by checking the mount setting and or updating disk driver. Find more solutions here.

Conclusion

The Mac recognizing the external HD is a delicate and complete process, any fault will lead to unrecognized hard disks. However, by checking the solutions one by one, the problem can be well solved.