How to fix unreadable USB flash drive on Mac and recover lost data?

Updated by Tim to Home > Mac Data Recovery Tips on March 24th, 2021

I stored the important data in USB flash drive, one day, when attempting to access it and I get a message: "The disk you inserted was not readable by this computer. There are three buttons: Initialize, Ignore, Eject"

The disk you inserted was not readable by this computer

Solution 1: Fix unreadable USB flash drive with Disk Utility

macOS built-in disk utility: First Aid has the ability to fix unreadable USB flash drive error.

Step 1: Open Applications -> Utilities -> Disk Utility.

Step 2: Select the unreadable USB flash drive.

Step 3: Run First Aid to fix the unreadable USB flash drive.

First Aid built-in Disk Utility

If First Aid fails to repair the unreadable USB flash drive, please go to solution 2 to recover lost data from unreadable USB flash drive.

Solution 2: Recover lost data from unreadable USB flash drive

As a professional USB drive data recovery software, M3 Data Recovery for Mac can recover lost data from unreadable hard drive, recover lost data from deleted/lost APFS partition, recover deleted files emptied from Trash, recover lost data from corrupted APFS drive,recover lost data from unmounted APFS drive, recover lost data from encrypted APFS drive, recover lost data from formatted drive, etc. on macOS 11 Big Sur/10.15 Catalina/10.14 Mojave/10.13 High Sierra/10.12 and Mac OSX 10.11/10.10/10.9/10.8.

Tutorial to recover lost data from unreadable USB flash drive

Step 1: Download, install and launch M3 Data Recovery for Mac software on your Mac computer.

Step 2: Select the unreadable USB flash drive.

Mac data recovery software

Step 3: M3 Data Recovery for Mac is scanning the data from unreadable USB flash drive.

Scan lost data from unreadable USB flash drive

Step 4: Select the found files you expect to recover and then click Recover to save them.

Recover lost data from unreadable USB flash drive

Solution 3: Fix the unreadable USB flash drive by reformatting

If USB flash drive doesn't important data, you can directly erase it and then it will be working again after the format completes. If there is important data, you can format the unreadable USB flash drive after data recovery is successfully done. Following is step-by-step tutorial to erase unreadable USB flash drive on Mac:

Step 1: Launch Disk Utility from Utilities.

Step 2: Click the icon for unreadable USB flash drive in the sidebar on the left.

Step 3: Click the Erase tab along the top of the window and enter the related information.

Erase the drive

Step 4: Click the Erase button.

Step 5: Click the Erase button to reformat unreadable USB flash drive, the unreadable USB flash drive will be working again after format completes.

Detailed tutorial: How to format USB flash drive on Mac?

Solution 4: Seek help from a local data recovery service

If USB flash drive is still not readable by any Mac data recovery software, please send it to a local data recovery service for help if you have important data.

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