Fix 'The disk you inserted was not readable by this computer' on Mac

1. Download and install EaseUS Data Recovery Wizard for Mac

2. Select and scan the drive/volume where you lost files

3. Preview the files and click the Recover button...Click full guide

Table of Contents

When Mac warns you "the disk you inserted was not readable by this computer", it means that your external hard drive or USB flash drive has a detect issue. You may follow the quick guide here fix this issue:

Workable Solutions Step-by-step Troubleshooting
1. Check Mac System Connect another external USB to Mac, check if it appears in Finder...Full steps
2. Check File System Check if the file system of your external device is NTFS. If yes, change it to FAT32...Full steps
3. Repair with Disk Utility Connect the external device to Mac > Go to "Utilities" > Select the device and click "First Aid"...Full steps
4. Initialize Disk Open Disk Utility > Choose problematic disk and click "First Aid" > "Repair disk" > "Erase"...Full steps

USB says 'the disk you inserted was not readable by this computer' 

"My Sandisk USB flash drive becomes unreadable and inaccessible for unknown reasons. Whenever I plugged it into my MacBook, I get the error message 'the disk you inserted was not readable by this computer.' I have many family pictures and working documents saved on the USB, is there any way to fix the flash drive and get access to my data?"

the disk you inserted was not readable by this computer

Fixes to 'The disk you inserted was not readable by this computer' error

  1. #1. Plug in Different Device to Mac
  2. #2. Check File System of Inserted Disk
  3. #3. Repair Unreadble Disk with Disk Utility
  4. #4. Initialize Disk and Recover Data

To open removable storage devices like an external hard drive, SD card, USB flash drive or even an Android phone or tablet, you usually have to insert it into a Windows computer or Mac. But if the system files or the disk is corrupted, error messages will pop up and prevent you access the device and data. In Mac OS X, the error message usually reads 'the disk you inserted was not readable by this computer.' 

Just like what happened in the story mentioned above, many Mac users have a similar experience of this issue and want to find a fix. Here, our advice about how to solve this problem is:

Step 1. Check the Mac system.

Just plug in a different external hard drive to Mac, if it appears on Finder, it suggests that the problem is related to the external USB devices, not the Mac. 

Step 2. Check the file system format

Check the file system format of the external hard drive, SD card, USB flash drive or other devices. If it is formatted with the NTFS format, then it is not hard to understand why it is unreadable on Mac. To correct it, please convert NTFS to FAT32. 

Disk formatting will erase data for good. It's good to back up the disk in question on Mac in advance with EaseUS Todo Backup for Mac.

Step 3. Verify or repair the unreadable disk, USB or SD card using Disk Utility

1. Choose "Go" > "Utilities".

2. Double-click "Disk Utility".

3. Select the volume in the left pane for which you want to repair permissions.

4. Click the "First Aid" tab.

5. Select the volume to which you want to install the Adobe application, and then click "Repair Disk" Permissions.

Step 4. Initialize the disk and recover data

If the problem continues, you have no choice but agree to initialize the disk you inserted as the pop up warns.

Care about important data? Please download and install EaseUS Mac data recovery software on your Mac because this fix will bring data loss on the storage device.

The overall troubleshooting steps are as follows:

1. Click on the "Initialize" button.

2. This will open Disk Utility. From the menu bar, click "View" > "Show All Devices". You can locate the problematic drive there, which Mac recognizes it as unformatted space.

3. Choose the drive from the left pane and click "Frist Aid".

4. Click "Repair Disk". Wait for the repair process ends. Can't repair disk because Disk Utility can’t repair this disk? Please continue.

5. Navigate to the "Erase" button. Name the drive and select "File Format" and click "Erase". This will format your drive with a correct file system.

After this, your Mac should now recognize the disk correctly. You will no longer receive such an unreadable disk error.

To recover formatted data on the disk, open EaseUS Data Recovery Wizard for Mac and follow this article: Recover Lost File from Formatted USB Flash Drive on Mac.

recover drive data on mac

If 'the disk you inserted was not readable by this computer' error still exists after trying all the methods, we recommend you to back up the drive always. Purchase a new device and be prepared for a drive failure soon.


On this page, we listed 4-step tutorial guide to help you fix 'the disk you inserted was not readable by this computer' error on Mac computer.

If you are having the same issue on your drive, follow tips on this page for help. Some of you may lose some useful files during the process and don't worry.

EaseUS Data Recovery Wizard for Mac can scan and find all your files in only a few clicks. It's your turn to make your drive work normally again.

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Updated by Daisy

Daisy is the Senior editor of the writing team for EaseUS. She has been working in EaseUS for over ten years, starting from a technical writer to a team leader of the content group. As a professional author for over 10 years, she writes a lot to help people overcome their tech troubles.

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Written by Roxanne

Roxanne is one of the main contributors to EaseUS and has created multiple posts on digital devices like PCs, Mobile phones, tablets, Mac, etc. She loves to share ideas with people of the same interest.

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