How to Fix the “Disk You Inserted Was Not Readable” Error

The disk you inserted was not readable

Your Mac may display the message “the disk you inserted was not readable by this computer”. This means the external device you’re plugging in and trying to use has run into an issue. It doesn’t always mean that it was a disk specifically that has caused an issue.

Do not worry though, there are ways to troubleshoot this issue. In this article, we’re going to talk about what you can do if your Mac displays this error to you.

First, let’s talk about what devices could be displaying these messages and why the external device isn’t showing up.

Why Isn’t My Device Showing Up?

Devices that we plug into our Mac have to interact with it and form a connection to transfer data between one another. Some of the most common devices that we plug in would be: external hard drives, SD cards, USD thumb drives.
Error disk was not readable

The reason behind why these devices aren’t working correctly varies as there are many things that could be causing them to not show up. Some of the most common reasons are:

  • The external device has suffered damage.
  • The ports on your Mac are dirty and need to be cleaned.
  • There may be either hardware or software issues causing us to receive this message.

When connected correctly, they should show up in the Finder sidebar as shown below.

drive list on mac

Before we attempt to fix the connection of the external device, let’s use Disk Drill to recover the data. Even though our Mac might not be able to see or use the device, Disk Drill might be able to see it recover data from it.

This will ensure that we get the data off of our device if there is an issue with it. If we continue to use the device, this can lower our chances of being able to recover data.

How to Recover Data From the Disk That Isn’t Readable

Disk Drill allows us to recover data from external devices if the hard drive is visible either in Finder or in the System Report section of our Mac. We can further check and see if the size that is being reported is correct which would confirm that we should be able to recover data from it.

We can plug our external device into our Mac and hopefully, Disk Drill can see it. In this example, we’re going to recover data from my external hard drive.

Step 1.Download and install Disk Drill onto your Mac.

Step 2.Plug in the external storage device that your Mac isn’t able to recognize.

Step 3.Launch Disk Drill and navigate to Storage devices or whatever the category is that your storage device falls under. Then click on Search for lost data.

select drive and start scan

Step 4.Wait for the scan process to complete.

scan in progress

Step 5.Once the scan has been completed, review the results and recover the data that is most important to you. There are some aviation videos of me flying in Utah that I want to recover. I navigated to the Video tab and then looked through the results to find the video that I wanted to recover. You can look at the thumbnail or click on the eye icon to preview the file. Checkmark the files that you would like to recover and then click on the blue Recover button to put the files back onto your Mac.

recover video with disk drill

That’s it! You can look at all of your files, pictures, videos, audio, documents, archives, and then other when using Disk Drill.

How to Fix “The Disk You Inserted Was Not Readable”

Now that we have recovered the data from our external device, let’s troubleshoot and try to fix the device.

There are many ways to troubleshoot our Mac and get the device to show up. Below, we will walk through the best methods to get our device working again. I would recommend that you follow these in order as they will be from the easiest and most practical to ones that will then require more steps and work.

Method 1: General Suggestions

There are some easy ways that we can troubleshoot our Mac right away that should fix the issue with the disk not being readable by this computer.

Power Down Your Mac and Then Turn It Back On

Turning our Mac off and then turning it back on is a super easy fix. Unplug your external device and then try the following.

Step 1.Go to the upper left-hand corner and click on the Apple logo.

Step 2.Select Restart… and your Mac will power down and back on again.restarting your mac

Step 3.Plug in your external device and see if it’s showing up now.

If your device isn’t showing up, let’s try cleaning out our ports.

Clean Out Your Ports

As we use our Mac, dust can get into our ports which could cause issues with our device not being able to connect to our Mac.

We can use compressed air to clean them out. I wouldn’t recommend that you use anything abrasive as you can damage your Mac and then it might need further repairs.

Connect to a Different Port on Your Mac

You can also try plugging your external device into another port on your Mac. There could be an issue with just one of the ports on your computer.

If you’re using a dongle to connect the device to your Mac, it could be causing the issue. Try using another dongle or take your computer into an Apple store and ask them to use one of theirs.

Replace USB Cables

Replacing the cable for your external device might help. A Google search of your device should help you figure out what cable it is using and then you can replace it.

Let’s move onto other methods if none of these fixed the issue for you.

Method 2: Reset NVRAM or PRAM on Your Mac

NVRAM (nonvolatile random-access memory) is a small amount of memory that your Mac uses to store certain settings and access them quickly. PRAM (Parameter RAM) stores similar information, and the steps for resetting NVRAM and PRAM are the same.

NVRAM stores things such as your sound volume, display resolution, startup disk selection, time zone, and recent kernel panic information.

If you experience issues related to these settings or others, resetting your NVRAM and PRAM might help.

Step 1.Shut down your Mac, then turn it on and immediately press and hold OPTION+COMMAND+P+R and hold these keys for about 20 seconds.

Step 2.Your Mac will then appear to restart. Let it boot up to the home screen and then login.

Step 3.Plug in the device that wasn’t working correctly and see if it works.

If you’re using a newer Mac that has a T2 security chip, you can release the keys right after you see the Apple logo.

If this didn’t fix your issue, let’s move onto resetting your SMC on your Mac.

Method 3: How to Reset the SMC on Your Mac

Resetting your SMC (system management controller reset) can resolve issues related to power, battery, fans, and other features of your Mac. This step will only apply to Macs that have an Intel processor.

This can fix the issue of your Mac not being able to see the external device that you’re plugging into your Mac.

Step 1.Shut down your Mac.shutting down your mac

Step 2.On your keyboard, press and hold the Control +Option + Shift keys.

Step 3.Keep holding down all three keys for 7 seconds, then press and hold the power button as well.resetting the smc on your mac

Step 4.Try plugging in your external device and see if it’s working correctly now.

If it’s not working still, let’s try and use First Aid to repair our device.

Method 4: Using First Aid to Repair Our External Device

First Aid is a repair utility that comes installed on your Mac as part of macOS. We can use it to repair things such as storage devices.

Step 1.Launch Disk Utility by going to the Applications folder and then the Utilities folder. After you’re within the Utilities folder, launch Disk Utility.

launch disk utility

Step 2.Once you have launched Disk Utility, select your external device and then click on First Aid.

selecting external hard drive in disk utility

Step 3.Run First Aid on the external device.

running first aid on an external hard drive

Step 4.Check and see if the device is working correctly.

Method 5: Formatting Your External Device

Sometimes troubleshooting doesn’t work and formatting the storage device is the last step. This will erase everything on the device and it will be set up like new again. While you do lose your data, this can fix issues when it comes to the external device not connecting.

Step 1.Launch Disk Utility by going to the Applications folder and then the Utilities folder. Once inside the Utility folder, launch Disk Utility.

Step 2.Inside Disk Utility select your external hard drive from the list of devices on the left-hand side. Then, click on Erase.

erasing external hard drive in disk utility

Step 3.Choose the format that you would like to format the external device to.

formatting external hard drive

Hopefully your external device is now working and you can start over fresh!


Knowing how to troubleshoot a Mac makes us a better computer user and can save us time and money. We have another article where we look into data recovery from a MacBook Pro that will overall enhance your ability to take care of your Mac should something go wrong.

By simply trying the steps in this article, it can also save us a trip to the Apple store as they will most likely attempt to fix the issue by going through what we just went through here together.