How to fix "The disk you inserted was not readable by this computer" on Mac?

By Katrina | Updated to Mac Data Recovery on June 28th, 2019 |

It is common that Mac reports "The disk you inserted was not readable by this computer" after you connected a USB flash drive, an SD card or an external hard drive to the Mac computer. This post explains the reasons why your drive was not readable and teaches you how to fix the issue without data loss. Download iBoysoft Mac Data Recovery to recover important files on the unreadable disk.

"The disk you inserted was not readable by this computer." is a common error message when you connected a removable storage device on Mac. If you are a Mac running Mac OS X and before, the error message looks like "The disk is unreadable by this computer. Do you want to initialize the disk on Mac?" I guess you were shocked when the tip came up. You probably had a lot of important work files and lovely family pictures stored on that external disk and you hadn't backed them up yet. did you sweat on the forehead because you were nervous about losing them for good?

The disk you inserted is not readable by this computer on Mac

Then you were confused when you saw the three button Initialize, Ignore and Eject, and didn't know what was the best move. Remember not to click on Initialize button but Ignore instead!

This post will explain the reasons why your disk was not readable on Mac and how to fix the unreadable disk issue without losing data.

Just keep reading.

Table of contents
1. Why is my disk not readable on Mac?
2. How do I fix an unreadable disk on Mac?
3. How to avoid disk not readable error?
4. Conclusion

Why is my disk not readable on Mac?

After you connected an external hard drive to a Mac computer, you may be told that the disk you inserted was not readable by this Mac computer. For example, your Mac computer could refuse to read the Seagate hard drive or other external disks. Why does this happen?

There are multiple causes for an unreadable disk:

  1. Out-of-date disk drivers. If you haven't updated your disk drivers for a long time, then the operating system couldn't send and receive data correctly to the disk you inserted, resulting in the disk unreadable.
  2. Encrypted drive. It makes sense that the Mac computer doesn't directly support a drive that is encrypted by a third-party encryption software or any native decryption tools in other operating systems. For example, Mac can't read Windows BitLocker encrypted drive.
  3. Corrupted file system. A file system is like an index or metadata that contains the information for describing the physical location, name, size, etc. of actual data. Therefore, once the file system with which the drive is formatted got corrupted due to improper operation, sudden power off, virus infections or physical damage, the operating system can't read the actual data on the drive.
  4. Damaged partition table. A partition table contains the information that describes where a partition starts and where it ends. With a damaged partition table, the operating system can't locate the partition and nor can read the data on the drive.
  5. The drive is APFS-formatted. Devices formatted with the High Sierra version of APFS will not be readable in previous versions of macOS. So, if you are using a Mac running macOS Sierra and before, it can’t read the drive.

When the disk was not readable, you were not able to open the disk. Therefore, you couldn't access the data on the drive at all. Then it was impossible for you to edit, transfer, save or delete files on it.

How do I fix an unreadable disk on Mac?

Before you start to fix "The disk you inserted was not readable by this computer" problem, one thing you should know is that there is no physical problem with your drive because at least it was detected. Then you can do a quick fix to see if your disk is readable again: reconnect the disk to the computer or change USB port or/and USB cable.

If your disk didn't even show up in Disk Utility, there could be some physical damage on your drive.

No matter what caused the unreadable disk issue on Mac, you are concerned about how to get your disk readable again and recover important files on it.

You can spend 2 minutes watching this video tutorial first:

Instead, you can also read the text tutorial as below to fix the unreadable disk on Mac:

Solution 1: Check if your drive is encrypted

Go to check if your drive is encrypted by a third-party encryption software or any native encryption tools. You need to decrypt the drive with the according decryption software first and mount it manually in Disk Utility.

For example, if you connect a Windows BitLocker-encrypted drive to a Mac, the error message "The disk you inserted was not readable by this computer" will occur because Mac doesn't support BitLocker. Therefore, you should turn off the BitLocker encryption on a Windows computer first so that the Mac can read it.

Solution 2: Update disk driver

An outdated disk driver could lead to an unreadable disk. Because a disk driver is too old, the operating system can't communicate well with the up-to-date external drive.

Here is how to update the disk drivers with a few clicks:

  1. Step 1: Click on the Apple icon at the left right corner and select System Preferences….
  2. Step 2: Click on Software Updates.
  3. Step 3: Click on Update Now or Update All if you have multiple updates.

Solution 3: Fix the unreadable disk with First Aid

As the corrupted file system can cause unreadable disk, so First Aid can be used to fix the corrupted file system. First Aid is a built-in utility that Mac computers have to check and repair minor file system problems on a drive including a local Macintosh hard drive, a USB flash drive, an SD card, an external hard drive, etc.

Follow the steps below to repair the disk that the computer didn't read with First Aid:

  1. Step 1: Go to Finder > Applications > Utilities > Disk Utilities.
  2. Step 2: Select the unreadable disk from the left panel.
  3. Step 3: Click the First Aid button at the top of Disk Utility window.
  4. Step 4: Click Run. First Aid will start to check the disk and repair it if necessary.

Repair unreadable drive with Disk Utility

But keep in mind that First Aid is only able to fix minor errors on a disk. If unfortunately, the file system of the disk is severely corrupted, First Aid could fail to fix the unreadable disk. Don't worry, let's move to the next solution.

Solution 4: Reformat the disk to make it readable again

If you can't fix the unreadable disk with the methods above, your disk must be seriously corrupted. In order to make a corrupted disk accessible again, the common way is to reformat the drive.

Please note that by reformatting or initializing, you will lose all the files stored on the drive. Thus, only do it directly if you don't have any important files on the drive or if you have a backup copy.

However, if you have important files without any backup, you need to at first recover data from the unreadable drive with a professional data recovery program, like iBoysoft Mac Data Recovery. Then, you can reformat it without worrying about data loss.

Recover data from the unreadable disk with free data recovery software

iBoysoft Mac Data Recovery is free data recovery software for Mac. It is capable of recovering data from unreadable USB flash drives, SD memory cards and external hard drives. With iBoysoft Data Recovery, photos, videos, documents, music, audios and emails can be retrieved from the unreadable disk with ease.

The utility supports data recovery in macOS 10.14 (Mojave), macOS 10.13 (High Sierra), macOS 10.12 (Sierra) and Mac OS X 10.11 (El Capitan), 10.10 (Yosemite), 10.9 (Mavericks), 10.8 (Mountain Lion), 10.7 (Lion).

Let's break down the data recovery process with iBoysoft Mac Data Recovery step by step:

Step 1: Download, install and launch iBoysoft Mac Data Recovery on Mac.

iBoysoft Mac Data Recovery

Step 2: Connect your USB drive/external hard drive/SD card to Mac.

Step 3: Select the unreadable drive and click Next. The program starts to scan for files on the unreadable disk.

Recover data from an unreadable disk with iBoysoft Mac data Recovery

Step 4: Preview the files at the left sidebar by double-clicking them after the scanning process is completed.

Note: The software provides two scan modes - Quick scan (Default) and Deep scan. If you don't see the desired files in the scanning results, click Back to home window and check Deep scan and hit Next to restart the scanning process for more files. If you want to recover files from an unreadable SD card, remember to check Deep scan first.

Step 5: Recover the file you want to recover by selecting it and clicking Recover button. Please save the recovered files onto another healthy drive.

Recover data from an unreadable disk with iBosyoft Mac Data Recovery

iBoysoft Mac Data Recovery is far more than an external drive recovery tool. It is capable of recovering data when the disk can't be mounted on Mac. Even when the Mac computer won't boot, it can help recover lost files from that unbootable mac. Additionally, iBoysoft Mac Data Recovery works great for retrieving important files from formatted/lost/inaccessible/corrupted drives or partitions too.

The steps to reformat the disk

If you have recovered all files with iBoysoft Mac Data Recovery, or you don't have any important files on the unreadable disk, it is time for you to get your drive accessible and readable by the Mac computer now.

Here is the procedures to take to make your Mac computer read the drive:

  1. Step 1: Go to Finder > Applications > Utilities > Disk Utilities.
  2. Step 2: Select the unreadable disk from the left panel.
  3. Step 3: Click the Erase button at the top of Disk Utility window.
  4. Step 4: Type in the name, choose a file system and hit Erase button.
  5. Step 5: Click Done after the reformatting is completed.
  6. Step 6: Reconnect the drive to the Mac or manually mount the drive in Disk Utility window.

How to avoid disk not readable error again?

Do you still chew on the shock and nervousness you have experienced when the error message "The disk you inserted was not readable by this computer" popped up?

In order to prevent that from happening again, here are some precautions you can take:

  • Eject the drive safely every time you finish using it on a computer.
  • Disconnect your drive first if you are going to turn off the computer or restart it.
  • Handle the drive with carefulness. Don't drop it hard or bounce it around, which can cause damage to the USB port, USB cable as well as the drive itself.
  • Back up your important photo files, video files, documents and other important files often. Even though your drive becomes unreadable suddenly, you won't be too hurry-scurry.

Conclusion

This post walks you through the process of repairing the unreadable disk and teaches you how to reformat the disk to make it readable again. Hopefully, you have fixed your unreadable disk on Mac successfully so far.

If you have a lot of important photos, videos, documents, music, audio and emails on the unreadable drive, do remember to recover them first with iBoysoft Mac Data Recovery to avoid permanent data loss.

Katrina

Katrina is a data recovery expert @iBoysoft who loves to help readers solve various data recovery problems.

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