How to fix "The disk you attached was not readable by this computer"

If your Mac says "The disk you inserted was not readable by this computer" when you connect your external drive, don't worry. It's often possible to recover and even continue using the drive. In this article, I'll show you how to fix a corrupted hard drive, make incompatible file systems readable, and prevent this error in the future.

Short on time? Easily find what you need with the solutions table.

Quick solutions to fix "The disk you attached was not readable by this computer"

What’s wrong?	How to solve?
Hardware issues	Test on another computer or change USB
Disk encryption	Decrypt the disk with password
Incompatible file system	Use iBoysoft NTFS for Mac
Malware	Scan and clean Mac using CleanMyMac
Disk corruption	Run Disk Drill to recover data

What's the "disk not readable" error?

The "disk not readable" error on a Mac occurs when macOS can't access or recognize an external hard drive or other storage device. This problem can be caused by incompatible file systems, disk corruption, or hardware problems such as faulty cables or connectors.

Essentially, the error prevents the drive from being mounted, making the data inaccessible without further troubleshooting or repair.

Reasons for Mac not reading external hard drive

Curious why this happens? Understanding why the "disk not readable" Mac error occurs is not straightforward and can vary from case to case. Anyway, here are the top reasons why your Mac is not reading the external hard drive:

• Disk failure: Sudden malfunctions may cause the drive to become unreadable.
• Hardware problems: Faulty hardware components or connections may prevent your Mac from recognizing the disk.
• Malware: Viruses or malware can interfere with the normal operation of external drives.
• File system compatibility: The drive may be formatted with a file system that macOS can't read.
• Improper shutdowns: Improperly shutting down your Mac could damage connected external drives.

How to fix it when your Mac is not reading external hard drive

Now that you have learned about the causes, you can try the following solutions to fix "The disk you attached was not readable by this computer." But before we get started, let me introduce you to Setapp.

Setapp is a subscription-based service that provides access to a curated collection of apps designed to streamline and solve various problems on Apple devices. Whether you're dealing with hard drive errors, file management, data recovery, or other system maintenance tasks, Setapp's suite of tools can make these processes much more manageable. Best of all, you can try all the 240+ apps for free for seven days, giving you the perfect opportunity to find the right tools for your needs without any immediate commitment.

Now, let's find out how to fix the disk not readable Mac issue.

Step 1. Do basic checks and troubleshooting 

The error that says your disk is unreadable comes with three options: Initialize, Eject, and Ignore. Before you click on any of these, it helps to do some basic troubleshooting. If you can fix the problem with basic troubleshooting, you won't have to repair or format your disk, which can cause data loss.

Check if the drive is the issue

The first thing you need to do is understand if the drive you're trying to connect to is the problem. Try unplugging the drive that's not readable and plugging in another external drive, USB, or SD. If it works, start investigating the problem with the first drive. If it doesn't work, look for hardware issues or other problems with your Mac. 

Make sure the disk is not encrypted

If the disk is the problem, check for disk encryption. Encryption means that the data on the disk is protected. If the disk is encrypted, you can't access it without decrypting it first. 

To check if your drive is encrypted on a Mac:

1. Connect your external drive to your Mac.
2. Locate Disk Utility in the Utilities folder in Applications, or use Spotlight (Command + Space) to find it.
3. Select your external drive from the sidebar in Disk Utility.
4. Check the encryption status. Look at the information displayed for the drive. If it's encrypted, you'll see it here.
5. If the disk is encrypted, you will need the decryption password to access its contents.

Check the file system

The most common reason your Mac won't read your drive is that it's formatted as NTFS. Since macOS doesn't have native read/write support, you'll need to convert NTFS to another compatible format.

Remember I talked about Setapp? Here's when you need it. On Setapp, you can find a tool called iBoysoft NTFS for Mac. It's an easy assistant with full read/write support for NTFS drives. 

You connect an external NTFS drive to your Mac, and that's basically all you do. The rest is pretty straightforward – access to your drive is right there in the menu bar. 

Check the disk on another computer

To further diagnose the "disk not readable" error, try connecting the drive to another Mac to see if it works there. Alternatively, you can try the drive on a Windows PC, which can help determine if the problem is related to the format of the drive. If the drive works on other computers, the problem might be with your Mac's settings or hardware.

Change the USB cable and USB port

To make sure the problem isn't related to the USB connection, first replace your current USB cable with one you know is working properly. Then, disconnect the drive from its current USB port and try connecting it to a different port on your Mac. This process can help you determine if the problem is with the cable or the port itself.

Step 2. Repair the drive using First Aid

If you're sure something is wrong with the disk and basic troubleshooting doesn't help, the next step is to try to repair the disk. 

The Mac has a native disk repair feature called First Aid. This is a completely safe process, and you can run it at any time to try to fix any misbehavior related to your disk. Specifically, if you see the problem "The disk you inserted was not readable by this computer," First Aid can help you check or repair permissions – the most common reason why the disk is not readable. 

Here's how to repair an external drive on a Mac: 

1. Shut down your Mac.
2. When turning it on, hold down Command + R.
3. Access Disk Utility from macOS Utilities at startup.
4. Select your drive in the left pane.
5. Click First Aid > Run. 

After the First Aid process is complete, you'll see a success message if the problem is fixed. Restart your Mac and try to reconnect your external drive or USB.

If First Aid didn't help fix the corrupted hard drive, you'll need to recover the data stored on the unreadable drive. See the next section. 

Recover files from a disk that isn't readable

I can imagine the sinking feeling you get when you see the "External hard drive not readable Mac" error, especially when important files are at stake. Fortunately, there's a simple solution – Disk Drill.

Disk Drill is a robust data recovery tool that you can access through Setapp. It's designed to recover lost data from almost any storage device, regardless of format.

Here's how to recover files with Disk Drill:

1. Download and install Disk Drill from Setapp.
2. Connect the unreadable disk to your Mac.
3. Open Disk Drill and select the problematic disk for a scan.
4. After the scan, review the files that can be recovered.
5. Select the files you need and restore them to another drive to avoid overwriting them.

I can't count the number of times Disk Drill has saved me by finding files I thought were gone forever. Give it a try!

Step 3. Format the drive 

While Disk Drill, the tool I've mentioned above, can recover files from an unreadable drive, it can't help you access and use it in the future. To make this possible, you should format the drive. This process basically wipes the drive clean and prepares it for initial use. 

Here's how to format an unreadable drive: 

1. In the error message, click Initialize.
2. When Disk Utility opens, select the drive in the left pane
3. Click Erase, select the right file system, and confirm that you want to format the drive. 
4. Reconnect the drive. It should now be readable. 

How to avoid the error in the future 

It's always better to prevent than to cure. Taking proactive steps to maintain your Mac and its peripherals can save you a lot of time and trouble down the road.

To avoid the "disk not readable" error on your Mac in the future:

• Maintain your external drives regularly. Use CleanMyMac to clean up junk files and repair disk permissions.
• Also, make sure your drives are ejected properly after use, and keep your Mac's software up to date to support newer file systems and improve compatibility.
• For advanced file system support, keep iBoysoft NTFS for Mac at hand, which provides reliable read and write access to NTFS formatted drives.

Note that all the tools mentioned in this guide – CleanMyMac, Disk Drill, and iBoysoft NTFS for Mac – are available on Setapp, a platform with macOS and iOS apps under a single subscription. Setapp offers you a free seven-day trial period for all of its apps, with no ads and no hidden fees. 

FAQ