How to Fix Corrupted External Hard Drives on Mac – Latest Guide

Mac users understand that it is expensive to change the SSD to add more storage to Mac computers. Purchasing a cost-effective external hard drive is the simpler option most people would like to adopt. But like other digital products, the external hard drive might stop functioning, get corrupted, fail to mount or read, or become inaccessible on a Mac. In light of this, we will go into detail on how to fix corrupted external hard drive on Mac. In this article, you will also learn how to recover lost data from the external drives on Mac step by step.

Part 1. How to identify whether an external hard drive is corrupted on Mac?

Logical errors that exist in the partition table or file system of the drive are what cause hard drive corruption on Macs. The following common issues will show up when you mount, access, or read a corrupted external hard disk on a Mac:

• The external hard disk you plugged in is not recognized by Mac.
• The “The disk you inserted is not readable” error message appears.
• The external hard disk won’t open, and you have no way to visit and use the files on it.

If you want to find out why the external hard drive got corrupted, you can go to “Finder” – “Applications” – “Utilities” – “Console” to access Mac Console and analyze the reasons through the report. In many cases, external hard drive corruption is caused by improper hardware connection, unsafe ejection, interruptions during file transfers, virus attacks, etc. 

Part 2. Fix a corrupted external hard drive on Mac (No formatting required)

If your external hard drive is not showing up on Mac Mini or MacBook Pro/Air, first make sure the connection between the device and the Mac is good. You can reinsert the portable hard drive into other USB ports, change a new USB cable or test this storage device on a different Mac to see if the computer can detect it.

If you are sure the physical connection between the hard drive and Mac is good, but macOS still does not recognize the device, you can try the following two workable methods to troubleshoot the issue.

2.1 Fix/repair a corrupted external hard drive using Disk Utility on Mac

Apple’s built-in Disk Utility can be used to perform disk (volume-related) tasks and repair the external storage device. For instance, a malfunctioning external hard drive, a faulty USB device, some apps closing suddenly, a corrupted file, or your Mac refusing to turn on. You can use the Disk Utility program to check the portable hard drive and fix minor file system corruption.

1. Open Disk Utility on your Mac computer (use Finder > go to Applications > Utilities > select Disk Utility.

2. Show all devices connected to this computer, and select the external hard drive that seems corrupted in the sidebar (check out the image below).

3. Finally, click on “First Aid” at the top, and click “Run.” Wait for a while since the repair process will cost a few minutes.

After DiskUtility successfully fixes the corrupted external drive, the device will appear on the desktop. If it is unable to repair the errors, you will see an error message “Disk Utility can’t repair this disk.”

2.2 Use the FSCK command to repair the external hard drive on macOS

FSCK (file system consistency check) is a useful tool for checking and repairing file system problems for your Mac’s internal disk and external hard drives.

In the event that Disk Utility First Aid and Mac Safe Mode fail to fix the external hard drive on Mac, you can use the FSCK command as an alternative.

Step 1. On your Mac computer, open Launchpad > Other > select Terminal.

Type the “diskutil list” command to list all the external drives that are connected to this computer

Step 2. Check the disk information and then find the malfunctioning hard drive you wish to fix and remember the drive identifier (It will have the format “disk2”, “disk2s1,” or “disk2s2”). You will need this information in the following steps, so either write it down or take a picture of it.

Step 3. Restart your computer and enter Single User Mode: When the boot process starts, hold down the COMMAND + S keys simultaneously. Hold down the Command and S keys until white text on a black background appears on the Mac screen.

Step 4. As soon as you input the correct user and password, some white text will scroll down. When it stops, type the following command below, and hit Enter key.

/sbin/fsck –fy

Step 5. Then type in the command below. (You need to replace “hfs” with your device’s actual file system and then use the correct drive identifier that you recorded in step 2. As the example image shows, it should be “disk2”, “disk2s1” or “disk2s2”.)

/sbin/fsck_hfs -fy /dev/[device’s drive identifier]

Step 6. After FSCK command finishes error repairing on your portable hard drive, type in “reboot” and press Enter key to reboot your Mac.

Part 3: How to recover lost data from corrupted external drives on Mac step by step

If you can’t repair the external hard drive using Disk Utility and FSCK command, the device is likely to be broken. In this case, you could reformat the drive so that it can be read by Mac and be used to store data again. Please note that formatting will inevitably erase all data from the drive. It is recommended that you recover all the important files from the corrupted Mac external hard drive before formatting it.

Professional-level data recovery software, such as iBoysoft Data Recovery for Mac, can restore lost data from external hard drives, no matter if the device is damaged, formatted, or unreadable.

Additionally, this useful utility can recover lost or deleted APFS partitions, restore files from unmountable macOS partitions, and recover lost files from USB flash drives, memory cards, SD cards, etc.

To recover lost data from unreadable external hard drives on Mac, here is what to do:

1. Download iBoysoft Data Recovery for Mac on the official website, install the app and then connect the corrupted hard drive to your Mac.

2. The software will list all the external devices. Now you can find and select the portable hard drive, then click “Search for Lost Data” to scan for all the recoverable files.

3. When data scanning is done, you can see the result and view the files which iBoysoft software found on this corrupted hard drive. 

4. Select a file and click Preview to check if that file is what you need, tick the box near the file, and finally, click Recover, and save it to a different external device.

Make sure that you have restored all the important files from the corrupted external hard drive. Then you can reformat the device to HFS+ or Apple File System (APFS) on Mac and use it again.