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

Home > HowTos > Troubleshooting Tips Updated by Nancy on May 24, 2024 | Approved by Christian Cawley

Encountering the error message "The disk you attached was not readable by this computer" and other similar tips on Mac can be frustrating and worrisome, especially when you need access to the files urgently. Whether it's an external hard drive, USB flash drive, or SD card, resolving this issue is crucial to regain access to your valuable data and ensure the usability of your storage device. This comprehensive guide, covering many troubleshooting solutions, will help you fix this error and provide preventive measures to avoid it.

Why Can't My Mac Read My External Hard Drive?

This error message of "the disk you attached was not readable" or "Mac the disk you inserted was not readable" indicates that your Mac cannot read the attached storage device for several reasons. The impact of this error includes loss of access to stored data, inability to transfer files, and potential data loss. Understanding the root causes behind this error is the first step toward effectively resolving it.

  • Cause
  • Description
  • Solution
  • 🔌 Connection issues
  • A faulty USB cable or port usually prevents the Mac from reading the inserted disk.
  • Method 1 | Method 10
  • 🔒 Encrypted Drive
  • Although encrypting the drive protects personal privacy and important files, it also prevents communication between it and macOS.
  • Method 2
  • ⛔ File System Incompatibility
  • This should be the main reason for such errors, especially the lack of compatibility with Mac for storage devices using the NTFS file system.
  • Method 3(Temporarily use tools to access the data without formatting)

    Method 9(Wipe your drive to convert the file system)

  • 🆕 A Brand New Disk
  • This may also cause an unreadable error. Please initialize it to assign the file system type and set the data storage and retrieval parameters.
  • Method 9
  • 💢 Corrupted File System or Data
  • It can also result in the "Disk You Attached Was Not Readable by This Computer" error message.
  • Method 5

    Method 6(For advanced users)

  • ⚠️ Outdated Drivers or Wrong Settings
  • When it fails, the communication bridge between the operating system and hardware components is blocked, leading to unreadable errors.
  • Method 4 | Method 7 | Method 8
  • 💽 Hardware Issues
  • Although such problems leading to read and write errors are rare, they are still possible.
  • Method 10

10 Ways to Solve "The Disk You Attached Was Not Readable by This Computer" Error

Although there are many reasons for such errors, don't worry. There are several solutions that can effectively resolve this issue. Let's take a look at the next!

1. Perform Basic Checks

Before delving into complex troubleshooting, it's worth doing a basic check of your storage device. They include:

2. Check if Your Drive is Encrypted

The "The disk you attached was not readable by this computer" error may be triggered when connecting a hard drive that is encrypted using third-party software such as BitLocker (Windows) or VeraCrypt to your Mac. To do this, please decrypt it before use.

3. Verify File System Compatibility

Common file systems that macOS supports include HFS+, APFS, ExFAT, and FAT32. If your USB drive's file system is NTFS, it will not be readable by your Mac. However, to convert a file system, you need to format it. But don't worry; there are still ways to access the data without formatting, like using a professional tool - Hasleo NTFS for Mac. It's completely free and easy to use. Here are the steps:

  1. Download and install this program on your Mac.
  2. After launching it, click its icon in the status bar.
  3. Click on your external hard drive and select "Mount."

After mounting successfully, you can perform read and write operations on this device.

4. Check the Drive's Permission Settings

Lack of read and write permissions can cause errors: the disk you inserted was not readable by this computer. Here are the steps to provide sufficient permissions:

  1. Right-click the external drive icon on the desktop and select "Get Info."
  2. In the Info dialog, locate the "Sharing & Permissions" section.
  3. Click the "🔒" at the bottom right and enter your login password.
  4. Select the desired permission level (e.g., Read & Write) from the dropdown menu.

  5. Eject and reinsert the drive to test for errors.

5. Use Disk Utility

macOS includes a built-in Disk Utility tool, which can help diagnose and repair disk issues. Here are steps to fix the error for the disk you attached was not readable:

  1. Find "Disk Utility" from the Applications > Utilities folder.

  2. Open it and select the unreadable disk from the sidebar.
  3. Click on "First Aid" and then "Run."

When this repair process is completed, you should be able to access your external hard drive correctly. The guide can also fix external hard drive very slow on Mac.

6. Try Terminal Commands

If Disk Utility fails to fix the issue, you can use Terminal commands to attempt repairs. Follow these steps:

  1. Open Terminal from the Applications > Utilities folder.

  2. Type "diskutil list" and press Enter. This command will list all connected disks and their identifiers.
  3. Type "diskutil verifyDisk /dev/diskX" (replace "diskX" with the actual disk identifier) and press Enter.
  4. If any errors are found, type "diskutil repairDisk /dev/diskX" and press Enter. This command will attempt to repair the disk.

7. Update the Drivers

Outdated drivers can render your disk unreadable. Here's how you can update drivers on your macOS:

  1. Click on the "Apple" icon in the top-left corner of the screen.
  2. Select "System Preferences" and click "Software Update."
  3. If updates are available, click "Update Now" to install them.

8. Reset NVRAM or SMC

NVRAM and SMC are responsible for managing system settings and hardware functions. A problem with these settings will also result in the error "Mac the disk you inserted was not readable." Here's how to reset it:

9. Initialize or Reformat the Unreadable Disk

If none of these DIY methods work, you may need to format an SD card or USB drive to resolve "The disk you attached was not readable by this computer." Keep in mind that reformatting will erase all data on the disk, so back up any critical files or use the following methods to recover the data before proceeding.

To fix an unreadable external hard drive on Mac, please follow these steps:

  1. Open Disk Utility.
  2. Select the unreadable disk.
  3. Click the "Erase" button in the toolbar.
  4. Choose a new format (e.g., APFS, HFS+, ExFAT, or FAT32) and enter a name for the disk.
  5. Click "Erase" to format it.

10. Seek Professional Help

Suppose the above troubleshooting failure. In that case, you can only seek professional help to repair underlying hardware issues or severe disk corruption with specialized tools and expertise. Therefore, please contact a reputable data recovery service or an Apple Authorized Service Pro.

How to Recover Data from the Unreadable Disk on Mac

The error notice for "The disk you inserted was not readable by this computer" will cause you to lose access to the data it stores. However, you can use Mac data recovery software to extract items. Here you can try iBeesoft Data Recovery for Mac:

Best File Recovery Software for Mac

(Trust Score 4.7 by 1695 Users)
  • Powerful retrieval capabilities: Even if your storage device is inaccessible, damaged, or formatted, it can still restore data.
  • Comprehensive File Recovery: It can recover many file types, including documents, photos, videos, music, archives, and more.
  • Multifunctional: It has built-in disk backup, file repair, and other additional options to protect your data security to the maximum extent.
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Steps to Resume Data When "The Disk You Attached Was Not Readable by This Computer":

  1. Visit the official iBeesoft website to download and install this program.
  2. Launch it and select the unreadable disk for the scan.

  3. After the scan, preview the recoverable files and select the ones you need.
  4. Click "Recover" to save them to a new location.

Tips for Preventing Future Disk Readability Errors

To prevent "disk you attached was not readable by this computer" errors in the future and ensure smooth data access on your Mac, consider the following tips:

Take these precautions; you can reduce the likelihood of encountering disk readability errors in the future.


Fixing the error message "The disk you attached was not readable by this computer" involves a series of troubleshooting steps, from basic checks to more advanced solutions like reformatting the disk. By understanding the causes and following the detailed steps, you can effectively resolve this issue and regain access to your valuable data.

Moreover, practicing proactive maintenance and regular data backups can help prevent similar unreadable disk errors in the future, ensuring your storage devices remain functional and your data stays safe.


  • This error typically occurs when your Mac cannot recognize or read the connected external drive. Several factors, including disk corruption, incompatible file systems, or hardware issues, could cause it.

  • Open the Disk Utility application located in the Utilities folder within Applications. If your disk appears in the list on the left, your Mac recognizes it, but a file system issue may prevent it from reading the data.

  • In Disk Utility, select the drive and look at the info pane to see its file system format. The 'the disk you attached was not readable' error may occur when the drive's file system is NTFS. You must reformat and select a compatible file system (e.g., FAT32, exFAT, HFS+, APFS) or use an NTFS tool to use it on a Mac.

  • Reformatting will erase all files on this disk. Back up your data before reformatting. If the drive is unreadable, use the best recovery software for Mac to retrieve data.

    1. DiskWarrior: Known for fixing hard drive problems.
    2. Drive Genius: Offers comprehensive disk management features.