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4. Mac Os Catalina Not Reading External Hard Drives

People use external hard drives as extended storage for computers or backup disks for important files, as a result, frequent file sharing, and modification are needed.If external hard drive suddenly shows read-only after you attach it to your Mac device, it is definitely very inconvenient to use this external hard drive. While this file system is readable on Macs because OS X can rearrange the data as it is reading it, the way that NTFS writes the files to the storage device is not; hence, you can read, but not write. The cause of the 'Read Only' behavior is due to the format of the file system. Many storage devices such as USB drives and external hard disk.

Summary: This post will show you 8 solutions to fix the disk unreadable error on your Mac.

Some users are experiencing 'The disk you inserted was not readable by this computer' error when connecting an external drive to their Mac computers.

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?'.

Even the disk unreadable error is encountered, how to fix this problem?

How to fix 'The disk you inserted is not readable by this computer'

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 disk has a problem:

Check if the disk is encrypted

If you receive the disk unreadable 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 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, 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 drive

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You can try simply re-connecting the 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 unreadable 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 disk unreadable error with Disk Utility

This error should be repaired using Disk Utility. It isn't guaranteed to work, but some users encountering the same error message have reported that 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 memory card, etc,.

Steps to fix 'The disk you inserted was not readable by this computer' error with First Aid:

Step 1: When the initial prompt 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 problematic 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 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 lost 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 lost 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.

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If the unreadable disk is encrypted APFS, 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 still not readable by M3 Data Recovery for Mac software, 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, audios. Click Preview button and check if your lost files are recoverable.

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Tips: If the above solution fails, return to M3 Data Recovery for Mac main interface 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 unreadable error.

Steps to repair the unreadable disk by initializing:

Step 1: Launch Disk Utility from Utilities in Applications folder.

Step 2: Select this unreadable disk at the left sidebar of Disk Utility.

Step 3: Click 'Erase' button in the toolbar of Disk Utility.

Step 4: Select file system and then click 'Erase' button, the unreadable disk will be working again after erasing.

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'?

Virus infection
Hardware issue
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

Mac Os Catalina Not Reading External Hard Drives

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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