[Fixed!] The Disk You Attached Was Not Readable by This Computer

“The disc you attached was not readable by this computer. Anybody run into this issue and have a resolution for it?”—Question from Apple Community

Today, we will talk about an error: “The disk you attached was not readable by this computer,” not allowing you to access data on the attached disk. Many Mac users have experienced this error when using external devices such as external hard drives, USB, and SD card on macOS Big Sur. Similarly, on macOS High Sierra, Mojave, and Catalina, you may as well face a variant error message: “The disk you inserted was not readable by this computer.”

The disk you inserted was not readable by this computer.

It is very frustrating, especially when you require important data. If you are one of the users who are confronted with these error messages, watching this article will help you solve it.

Why the disk you attached was not readable?

It is essential to understand what caused the “the disk you attached was not readable by this computer” error. There are a lot of reasons that can result in it, directly or indirectly. It is hard to tell what exactly causes this error. Below are the probable causes that we outlined. 

Connection IssuesThe possibility exists that there is a poor connection due to damaged ports, USB cables, power supply, or the device being locked.Have Basic Troubleshooting
Outdated macOSIf you use the latest macOS, you use the newest driver. An outdated macOS may be a possible reason for the disk being unreadable.Update Your macOS
Disk FailureFile system corruption, partition loss, disk encryption, or any other logical error that happens to the disk can make the computer unable to read the disk.Run First Aid 
Uninitialized DiskAn unformatted disk with an unsupported file system/uninitialized new disk is a probable reason. Initialise (format) the Disk 
Malware infectionA Malware infection of your Mac can cause the system not to read the disk. Malware Check
Physical Damaged DiskAnother probable reason is that your disk device is physically damaged, which is not readable by the computer.Have Basic Troubleshooting; Find Professionals

How to fix the disk you inserted that was not readable by this computer?

Now that you have learned what causes the disk you attached to not be readable by this computer, Here are six solutions you can try one by one to get this error resolved.

1. Have Basic Troubleshooting

Before doing some complex steps, try these basic troubleshootings.  

Basic TroubleshootingDescription
Examine your external device🔌Make sure there is no apparent damage and no bends in appearance on your external hard disk or other devices. Try to connect it to the Mac directly, not using an adapter/converter or any USB hub, if possible. 
Check the encryption🔐Check if the device is or is not being locked or have the encryption turned on.
Restart your Mac🖥️A simple restart can sometimes fix minor, one-time bugs and glitches that may cause this error.   
Reconnect the Device📺Like restarting your Mac, a reconnection has a chance of solving this error. 
Check the power, port, and cable🔋Make sure the proper connection and normal power supply. Try to use another outlet, port, or cable to connect the Mac to see if it is going to work. 
Use another Mac💻You can try to use another Mac to see if the error still exists. This will determine whether the error is caused by your computer or external device. 
File System Format Check📋Check if the file system of the device is or is not supported by macOS on the File system formats available in Disk Utility on Mac.

2. Update Your macOS

You don’t need to update your drivers separately like doing it on Windows. Because macOS handles all systems and drivers. For instance, the graphics drivers, and the disk drivers are built into the macOS. You update the macOS, equivalent to updating the drivers. 

  • Step 1. Click the Apple icon in the menu.
  • Step 2. Click System Preferences.
Click System Preferences
  • Step 3. Click Software Update.
Click Software Update
  • Step 4. If there is any update available > click Update Now or Restart Now to update.
click Update Now or Restart Now to update.
  • Step 5. Your Mac will restart after updating > check if this error still persists. 

3. Run First Aid

First Aid is a built-in utility on Mac that can help you check and fix file system errors on external devices.

  • Step 1. Go to the Applications.
  • Step 2. Click Utilities > Disk Utility.
Click Utilities > Disk Utility.
  • Step 3. Click View to view all the devices, and choose the unreadable device. 
Click View to view all the devices
  • Step 4. Click the First Aid button on the top.
Click the First Aid button on the top.
  • Step 5. Click Run to confirm your decision. > Click Continue to confirm again.
Click Continue to confirm again.
  • Step 6. This will take a little time. > This procedure may fail; restart your computer and do it again.
restart your computer and do it again.
  • Step 7. Check to see if this error still persists.

4. Malware Check

Users believe that Mac doesn’t get any Malware or viruses, wrong. Like on Windows computers, the virus is still a big threat to data security on Macs. If your Mac is infected with malware, your Mac will behave erratically, including “the disk you attached was not readable by this computer. “

  1. Update your antivirus software to the latest versions if you have one.
  2. Manually check for viruses.
  3. Delete suspicious apps.
  4. Here are the top antivirus for Mac on Forbes: Best Antivirus For Mac Of 2023

5. Initialize the Disk

If you are using an uninitialized new disk or the format of the disk is not APFS (Apple File System) or Mac OS Extended (Journaled), Mac likely cannot read it. So, you need to format or initialize the disk into an APFS or Mac OS Extended (Journaled) disk. Initializing your external disk is the last way to fix the unreadable error. This solution is going to erase all the data inside the device and set the device brand new again. 

For the difference between APFS and Mac OS Extended (Journaled):

APFS format is used for macOS Mojave or later.

Mac OS Extended (Journaled) is used for macOS High Sierra or older versions. 

  • Step 1. In the error message “The disk you attached was not readable by this computer,” click Initialize. 
click Initialize.
  • Step 2. The Disk Utility will be opened.  
  • Step 3. Click View> Show All Devices. > Choose your device volume.
  • Step 4. Click the Erase button on the top.
Click the Erase button on the top.
  • Step 5. Give a name to the disk. > Select the file format, you can choose APFS or Mac OS Extended as the file format. > Click the Erase button.
Select the file format
  • Step 6. After the formatting is done, you can access the disk.

6. Find Professionals

If you are worried your action will cause further damage to your computer or your external storage devices, or if you try the above solutions but none of them are working, you can seek professional help. They will help you solve this error. Please note this may be charged. 

Bonus Tip: How to recover data on an unreadable disk?

If the storage device is not readable, you can not access the data on it. You can recover your data from a backup file if you have backuped it. If you don’t,  the best DIY way to recover your data on an unreadable storage device is using recovery software. 

For this, here we go ONERECOVERY for Mac. It has full compatibility with macOS Sonoma, macOS Ventura, etc., with M1, M2 & T2 chips. This professional but user-friendly data recovery software helps you retrieve lost/corrupted/deleted data with simple clicks.

onerecovery for mac
  • Launch the software and scan the drive volume on which the data is lost.
scan the drive volume.
  • Preview the recoverable data and choose the file you want to recover.
Preview the recoverable data
  • Recover it to a new place.

FAQs on the disk you attached was not readable

Q1: How do I fix an unreadable SD card on my Mac?

1. Use a different card reader.

2. Check the physical lock switch on the body.

3. Run First Aid.

4. Format the card.

Q2: What is “the disk you inserted was not readable by this computer”?

This means the external storage device you connect to the computer can be detected but cannot be read. The data is inaccessible. 

Q3: How do I fix a corrupted hard drive on a Mac?

1. Update your macOS.

2. Run first aid.

3. Have a malware check.

4. Initialize the hard drive.


We listed six solutions for you to solve “The disk you attached was not readable by this computer” on Mac. No matter what error message shows up on your screen, as long as it is related to the unreadable device, the essence is the same. To avoid external storage devices being unreadable on your Mac, you better perform good maintenance of your device, such as doing safe ejection, regularly checking for malware, etc. For your data security, it is suggested that you backup your data on time. As for any other problems, feel free to contact us.