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Some users encounter the error “The Disk you Inserted was not Readable by this Computer” when connecting an external drive to their Mac computers.
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From Big Sur through macOS Tahoe, the alert usually reads “The disk you attached was not readable by this computer.” The fixes are the same.
This problem occurs most often on macOS, but it also occurs on Mac OS X with a different message “The disk is not readable by this computer, do you want to format the disk?”
So what actually causes the unreadable disk error, and how do you fix it without losing your files? Let’s go through it step by step.?
How to fix “The disk you inserted was not readable by this computer”
Quick answer: click Ignore, not Initialize. Then check the cable and port and run First Aid in Disk Utility. If First Aid fails, recover your files first and only then erase the drive.
Solution 1: Perform the basic troubleshooting
There are six ways to troubleshoot a basic problem and determine if the disk is problematic:
Check if the disc is encrypted
If you receive the unreadable disk error after inserting an encrypted drive, then you need to open that drive with the corresponding application.
For example, if the disk is encrypted by BitLocker, macOS also reports “The disk you inserted is not readable by this computer” without installing the BitLocker tool for Mac. In this case, you’ll need a third-party BitLocker reader for macOS, or you can unlock the drive on a Windows PC and copy the files off there.
Check if the file system is incompatible with macOS
Check the file system for your external drive to see if the file system is compatible with macOS. If macOS doesn’t support this file system, that Mac won’t read the disc you inserted. For example, macOS does not support the ReFS file system. macOS reads APFS, HFS+, exFAT and FAT32 (NTFS is read-only), but not ext4.
Check if the disk is a new hard disk
If it is a new hard disk with nothing on it, click the “Initialize” button (older versions of macOS called it “Format”) to format this disk after seeing the unreadable disk error. After formatting, this new hard drive will work.
Check the disk on another computer
Connect this unreadable disk to another Mac and check if it can be read. If this error persists, then try other solutions as follows.
Change the USB cable and the USB port
Sometimes there is a problem with the USB cable or the USB port, so this computer cannot read the disc you inserted. In that case, please change another USB cable or USB port and try again.
Reset the USB port
If you are sure that the USB port is a problem and not the device, the first thing you need to do on an Intel-based Mac is to reset the SMC (System Management Controller). Macs with Apple silicon (M1 and later) don’t have a separate SMC reset. A simple restart does the same job.
Solution 2: reinsert the drive
You can simply try to reconnect the hard drive to your Mac. Just safely remove it from your Mac then reconnect it. Then try to access it and see if the error persists. If this error persists, go ahead and try the next solutions.
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Solution 3: Update macOS to get the latest drivers
The unreadable disk error can also be caused by an outdated driver on your Mac. On a Mac, driver fixes arrive with macOS updates. You can check and update the drivers on your Mac by following these steps:
- Go to the Apple menu and select System Settings (called System Preferences on macOS Monterey and earlier).
- Click General, then Software Update.
- Check if any updates are available for your system and apps.
Solution 4: fix the unreadable disk error with Disk Utility
This error should be fixed with Disk Utility. It’s not guaranteed to work, but some users who encountered the same error message reported that the problem was resolved.
First Aid is a utility built into Mac OS. You can check and fix file system errors on Macintosh HD, external hard drive, USB drive, flash drive, SD memory card, etc.
Steps to correct the error “The disc you inserted is not readable by this computer” in First Aid:
- When the initial message appears, tap Ignore to ignore it.
- Once the error is dismissed, open Applications -> Utilities -> Disk Utility.
If the Macintosh HD is unreadable, run First Aid from macOS Recovery. On a Mac with Apple silicon, shut down, then press and hold the power button until you see “Loading startup options,” click Options and choose Disk Utility. On an Intel Mac, restart and hold Command + R.
- Choose View > Show All Devices, then select the problem disk in the sidebar.
- Click the “First Aid” button on the Disk Utility toolbar.
- Click Run. First Aid will check the volume for errors and fix the problem if possible.
Wait for the procedure to finish. If First Aid says the disk is OK or has been repaired, eject it, reconnect it and see if it mounts. See Apple’s Disk Utility repair guide.
If another message indicates that Disk Utility cannot repair the unreadable disk, go to Solution 5 to recover the lost data.
Solution 5: Recover data from the unreadable disk
If First Aid can’t fix the drive and the files matter, get them off before you try anything else, especially formatting. The simplest route is a backup:
No backup? A reputable Mac data recovery tool can often scan a drive that Finder refuses to mount, Install it on your Mac (never on the problem drive), scan the disk, preview what it finds, and save recovered files to a different drive.
If the drive clicks, grinds or isn’t detected at all, stop using it and take it to a professional recovery service.
Solution 6: format the unreadable disk
After successfully completing the data recovery, it is time to clean this disk to fix the unreadable disk error.
Steps to repair an unreadable disk by formatting:
- Launch Disk Utility from Utilities in the Applications folder.
- Choose View > Show All Devices and select the unreadable physical disk (the top-level entry) in the left sidebar of Disk Utility.
- Click the “Erase” button on the Disk Utility toolbar.
- Pick a name and a format, then click Erase. Choose APFS for a drive you’ll only use with modern Macs, or exFAT if it also needs to work on Windows PCs. The unreadable disk should work again once it’s erased.
Solution 7: Seek help from a professional
However, some users may be concerned that their improper operations will cause more damage to their hard drives. In this scenario, it is best to take it to a local professional. They can make some correct suggestions to get rid of this error.
Solution 8: consider replacement
If you don’t need the data and the drive is still under warranty, you will need to replace it or request a refund.
Why does a Mac say “The disk you inserted was not readable by this computer”?
macOS can see the drive but can’t make sense of what’s on it. Common triggers:
- Virus infection
- Hardware problem
- The disk is not formatted
- Catalog file is corrupted
- The disk structure is damaged
- The file system is corrupt
- Force restart the computer
- Disk File System is incompatible with macOS
- Disconnect or close the unit without dismantling it
- Experiencing a program hang while writing to the drive
- Shutting down the computer without performing a proper shutdown
- Disk failure – The disc itself or its USB interface may have failed. In this case, a data recovery solution is recommended.
Which fix should you try first?
When you see “the disk you inserted was not readable by this computer,” I’d start with the free, safe checks: a different cable and port, then Disk Utility First Aid. Recover important files before erasing. And if the drive is new or empty, initializing it is the quickest fix.
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