Fix "The disk you inserted is not readable by this computer" on Mac
Summary: This post will show you 8 solutions to fix the disk not readable error on your Mac.
Some users are experiencing "The disk you inserted was not readable by this computer with Initialize, Ignore and Eject button" error when connecting an external hard drive, SD card, USB flash drive to their Macs with macOS Catalina, Mojave or High Sierra installed.
While macOS Big Sur users are receiving the different error: "The disk you attached was not readable by this computer" with Eject, Ingore and Initialize button.
Some affected users report the issue occurs with every external drive. While others say this unreadable disk error only appears with one external drive.
Most of the time, this issue happens on macOS, but it also occurs on Mac OS X with a different message "The disk is unreadable by this computer, do you want to initialize the disk?".
Once the disk not readable error is encountered, how to fix this problem?
How to fix "The disk you inserted is not readable by this computer" on Mac
There are eight solutions to fix "The disk you inserted is not readable by this computer" issue on your Mac:
Solution 1: Do a basic troubleshooting
There are six methods to do a basic troubleshooting and determine if the unreadable disk (External hard drive, SD card, USB flash drive, etc.) has a problem:
Check if the disk is encrypted
If you receive the disk not readable error after inserting an encrypted drive, you need to open this drive with the corresponding app.
For example, if the disk is encrypted by BitLocker, macOS also reports "The disk you inserted is not readable by this computer" without BitLocker for Mac tool installed. In this case, try M3 BitLocker Loader for Mac to access BitLocker encrypted drive on Mac.
Check if the file system is not supported by macOS
Check the file system of the external drive to see if the file system is supported by macOS. If macOS isn't compatible with this file system, the disk you inserted is not readable by this Mac. For example, ReFS file system is not supported by macOS.
Check if the disk is a new hard drive
If it is a new hard drive, click "Initialize" button to initialize this drive after seeing the unreadable disk error. After initializing it, this new hard drive will be working.
Check the disk on another computer
Plug this unreadable disk into another computer (Windows or Mac) and check if it can be readable. If this error continues, try other solutions as below.
Change USB cable and USB port
Sometimes, USB cable or USB port is something wrong so that the disk you inserted is not readable by this computer. In this case, change another USB cable or USB port and try again.
Reset USB port
If you're confident USB port is a problem and not the device itself, the first thing you should do is reset SMC. It is a simple process which is slightly different depending on the Mac hardware.
Solution 2: Re-insert the external hard drive
You can try simply re-connecting the external hard drive to your Mac. Just safely remove it from your Mac and then re-plug it. Then, attempt to access it and see if the error persists. If this error still occurs, please move on and try following solutions.
Solution 3: Update the drivers on your Mac
The disk not readable error can also be caused due to an outdated driver on your Mac. You can check the drivers on your Mac and update them via the following steps:
Step 1: Go to Apple menu and select "System Preferences..".
Step 2: Click "Software Update".
Step 3: Check for any available updates for your system and applications.
Solution 4: Fix the unreadable disk with First Aid
The disk not readable error should be repaired using First Aid. It isn't guaranteed to work, but some users encountering the same error message have reported the issue was resolved.
First Aid is a utility built-in Mac operating system. It can check and repair file system errors on Macintosh HD, external hard drive, USB drive, flash drive, SD card, etc,.
Steps to fix the unreadable disk with First Aid:
Step 1: When the initial prompt message "The disk you inserted was not readable by this computer" appears, click Ignore to dismiss it.
Step 2: Once the error has been dismissed, open Applications -> Utilities -> Disk Utility.
If Macintosh HD is not readable, please run First Aid from recovery mode. Restart your Mac and press & hold down Command + R keys at startup, then select Disk Utility from macOS Utilities panel.
Step 3: In the left panel of Disk Utility, select the unreadable disk.
Step 4: Click "First Aid" button in the toolbar of Disk Utility.
Step 5: Click "Run" button, First Aid will check the volume for errors and then fix the problem on the unreadable disk if possible.
Wait until the procedure is complete. If you get returned a message saying success, restart your Mac and see if the disk becomes readable.
If another message says that disk utility cannot repair unreadable disk, go to solution 5 to recover data.
Solution 5: Recover data from the unreadable disk
Due to the above causes, macOS fails to read the disk and you cannot access the data stored in it. To access the data, you can restore your data from the backup if you have a backup elsewhere. If you do not have a backup, you need a professional Mac data recovery software to recover data, such as M3 Data Recovery for Mac.
As a professional Mac data recovery software, M3 Data Recovery for Mac can recover files from the unreadable drive, formatted drive, even recover deleted files emptied from Trash, recover data from deleted/lost APFS partition, etc.
M3 Data Recovery for Mac is fully compatible with macOS Big Sur 11/Catalina 10.15/Mojave 10.14/High Sierra 10.13/10.12 and Mac OS X 10.11/10.10/10.9/10.8.
Tutorial to recover data from the unreadable disk on Mac
Step 1: Download, install and launch M3 Data Recovery for Mac software on your Mac.
If the Macintosh HD is unreadable, you need to run M3 Data Recovery in macOS Recovery mode.
Step 2: Select the unreadable disk and click Next to continue.
If the unreadable disk is encrypted APFS file system, click "Find Lost APFS Partitions" at the top to recover data from the encrypted APFS disk. The encrypted APFS drive data recovery requires the password to decrypt the data.
Step 3: M3 Data Recovery for Mac software is scanning the data from the unreadable disk.
If the disk is not readable by M3 Data Recovery for Mac software either, send it to a local specialist for data recovery help.
Step 4: After the scan completes, you can preview the documents, photos and play videos, audio. Click Preview button and check if your lost files are recoverable.
Tips: If the above solution fails, return to the main interface of M3 Data Recovery for Mac and choose the volume to scan again.
Step 5: Select the files you need and click Recover to start the recovery.
At this step, you need another drive to save the recovered files.
Solution 6: Initialize the unreadable disk
After data recovery is successfully done, it is time to erase this disk to repair the disk not readable error.
Steps to repair the unreadable disk by initializing:
Step 1: When the initial prompt message "The disk you inserted was not readable by this computer" appears, click "Initialize" to open the Disk Utility.
Step 2: Once Disk Utility is open, you will see a list of drives attached to the system. Select the problematic disk you wish to initialize.
Step 3: Click on the "Partition" tab.
Step 4: Now click on "Options" to select the partition scheme for the drive: GUID partition table, Apple partition table or Master Boot Record.
Step 5: After clicking "OK", need to partition the drive. You can create multiple partitions if you want.
Step 6: Select what file system to use.
Step 7: After selecting the file system and clicking "Apply", you will be presented with a confirmation dialog.
Step 8: After clicking "Partition", Disk Utility will format the drive.
After the formatting process is complete, you can access this disk as normal.
Solution 7: Ask a professional for Help
Nevertheless, some users may worry that their own improper operations will make the further damage to their hard drives. In this scenario, you'd better take it to a local professional. They could give you some correct suggestions to get rid of this error.
Solution 8: Consider a replacement
If you don't need the data and the drive is still within warranty, you will want to have the drive replaced or ask for a refund.
Why does Mac say "The disk you inserted was not readable by this computer"?
The disk is not formatted
Catalog file corruption
Disk structure is corrupted
File system is corrupted
Forcing a restart on the computer
The file system of the disk is not supported by macOS
Disconnecting or power off the drive without unmounting it
Experiencing a software lockup while writing to the drive
Turning the computer off without doing a proper shutdown
Disk failure - It is possible that either the disk itself or just its USB interface has failed. In this case, a data recovery solution is advisable.
How to avoid disk not readable error again
1. Eject external drive properly
External drive is easy to be corrupted if you eject the external drive improperly. If you remove external drive from the computer when being in use, it can also be corrupted. So you must safely remove your external drive from the Mac by clicking "Safely Remove Hardware" option.
2. Back up important data
Data backup is the best way to prevent data loss. Time Machine is a macOS built-in data backup software which can automatically back up all of your files.
3. Use advanced file system
If you have a choice, please adopt NTFS (APFS, HFS+) file system instead of FAT32/exFAT file system. NTFS file system gives you more flexibility in length of filenames and directory, security control. What's more, you can stand a greater chance of recovery in case of drive corruption.
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