Fix “The disk you inserted was not readable by this computer” error on Mac

In this tutorial we’re going to show you how to troubleshoot issues with your USB flash drives(USB drive/external hard drive/SD Card) and also hard drives not showing up on your Mac computer. Error message “The disk you instert was not readable by this computer” will pop up.

Step 1: Make sure Mac detected your drive

First thing, we need to make sure that the drives are actually having some kind of hardware, it’s at least being detected by your Mac. To do it, we’re gonna do is we’re going to go to the system information. Double click applications, and then go to utilities, and then system information.

Mac system information window

We’re trying to do is make sure the system detects the drive. Just look all the way down the list at left, looking for USB. Click the USB at left menu, you should see you drive on right.

USB flash Drive detail window (Mac)

If you do not see your drive listed here, disconnect the drive and then plugging it into an alternate USB port and try to access system information again, check if the USB drive shows up. If alternate USB port works, the first USB port you use may broken.

Step 2: Show USB drive on your desktop and finder window

Next we’re going to go to the easy approaches. Because ordinarily when you plug it in, it’s going to show up on the desktop or it’s going to show up and finder window. Go to Finder, click preferences. And then go to the General tab. Under “Show These Items on the desktop”, make sure external disks checked. Then go to Sidebar tab, under Devices section make sure you have the external disks check. Now USB drive should show on your desktop or Finder window automatically.

Set up finder preference to show USB drive on desktop or Finder window automatically

Step 3: Fix your USB disk with Mac Disk Utilities

If the drive is still not showing up, next plan is going to be with utilizing the Disk Utilities. Back to applications again, and then go to utilities at the bottom of applications window.

Mac Disk Utility Window

The Disk Utilities is for situation like the drive actually is detected but you still have trouble accessing the contents of it. Just clicking on the drive, click on “First Aid” and then click run button. It’s going to automatically repair any of the errors on the drive. After “First Aid” finished, unplug the disk, wait 10 to 15 seconds and plug it back in, try to access it again.

Launch Disk Utility, select the unreadable USB drive/exteral hard drive/SD card, then click “First Aid” button

Step 4: Try access your USB drive in another computer

If the drive still is not detected properly or it’s detected but you still cannot access the data on it, the next thing you can do is, try it in another system. Try this disk in another Mac or possibly a PC, to see if it actually is detected correctly and if you can access the data. Go ahead and copy off all your data as much as you can. Always backup all data when you can access this USB drive.

Final step: Recover data and format your USB drive

Finally, if none of these working for you, try recover data from your USB drive with Mac data recovery software, then format the unreadable drive. The recovery software will recover data to your hard disk, and you can format your USB drive so you can access it again. However, you strongly recommend you don’t copy any important data on this USB drive again because it may already broken.

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