What Is the ‘Data Couldn’t Be Read Because It Isn’t in the Right Format’ Error?

New Mac operating systems often have errors that frustrate users, despite going through a QA process. This is partly due to differences between the number of beta users and actual installations. The technical details may not be easy for all users to understand.

In this guide, we will look at one common problem that frustrates users, especially after updating to Mojave: the error “Data couldn’t be read because it isn’t in the right format.” With patience and a little bit of luck, you might be able to correct the issue yourself or prevent it from happening again.

Error ‘Data Couldn’t Be Read Because It Isn’t in the Right Format’ After Updating to Mojave: The Cause

There are many possible reasons why you are getting the “Data couldn’t be read because it isn’t in the right format” error. But as the name of the error suggests, it is likely that Mojave is not able to read data because its file format is not supported.

Along with the launch of macOS High Sierra in 2017, Apple also introduced a new file system called Apple File System (APFS). Since then, it’s been implemented and used on various Apple devices, such as iPads, iPhones, Macs, and MacBooks.

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This file system format was released with two primary goals. First, Apple seeks to offer a quicker and more efficient experience for users. Second, they want macOS and iOS to have a uniform file system for future growth.

Installing High Sierra or updating to Mojave will automatically make changes in your main hard drive’s current file system. However, it won’t do the same with the files on your external drives. This only means you need to convert the files yourself. Otherwise, you might see the error pop up.

Now, how do you fix this annoying problem?

How to Fix ‘Data Couldn’t Be Read Because It Isn’t in the Right Format’ Error

To fix or keep “Data couldn’t be read because it isn’t in the right format” error from showing, you might need to convert all your drives, regardless whether they are HDDs or SSDs. You have two options to do this: use Disk Utility or use Terminal.

Convert to APFS via Disk Utility

If you are converting an external drive, you can use Disk Utility to convert it to APFS format. Here’s how:

  1. Connect your external drive to your Mac or MacBook. Make sure the connection is not loose, else it might not be detected.
  2. Next, open Disk Utility via Spotlight. Press the CMD and Space keys to launch Spotlight. In the text field, input Disk Utility.
  3. Highlight the drive you wish to convert by clicking on it.
  4. Navigate to the Edit menu and select Convert to APFS.
  5. Depending on the size of your external drive, the conversion processing time varies. But it should not take hours. Once complete, your external drive should run on Apple’s new APFS format.

Convert to APFS via Terminal

If you are converting an internal SSD to APFS format, then you should use Terminal. Follow the steps below to know how:

  1. Make sure your SSD is properly installed into your computer.
  2. Boot your computer to internet recovery mode using the CMD + Option + R keys. Hold them until you see a globe. Wait for the boot sequence to be completed. It might take up to 15 minutes to finish, depending on your internet speed.
  3. The macOS Utilities menu will show after. Select Disk Utility.
  4. Open the View menu and click Show All Devices. Your SSD should show in the left column. If you don’t see it, quit Disk Utility and open it again.
  5. Close Disk Utility. From the Menu bar, hover over the Utilities menu and click Terminal. Here’s a friendly reminder. Do not attempt to disconnect any external drives at this point to prevent corrupting the data on them.
  6. In the Terminal, input the command below and press the Return key:

diskutil list

  1. The command should pull a long list of disks that are mounted on your computer. To identify an internal SSD, look for the words “(internal, physical)” in the description. After identifying the SSD, take note of its identifier. It’s usually named “disk0,” “disk1,” “disk2,” and so on. You’ll need the identifier in the next step.
  2. Input the command below along with its identifier, and then press the Return key:

diskutil eraseDisk JHFS+ MacOS /dev/identifier

  1. The process may normally take minutes to complete. You’ll know it’s done when you see the message “Finished erase on identifier” and when the SSD is now named MacOS.
  2. Next, take note of the new identifier of the SSD. It is usually mentioned in the line that says, “Formatting identifier as Mac OS Extended (Journaled) with name MacOS.”
  3. In the Terminal, enter the command below and press the Return key:

diskutil apfs createContainer /dev/identifier

  1. Again, the process may take minutes to complete. Once it’s done, you will see the message “Finished APFS operation on identifier MacOS.”
  2. Now, take note of the new identifier for the final Terminal command.
  3. In the Terminal, enter the last command and press the Return key:

diskutil apfs addVolume identifier APFS MacOS

  1. The process may take minutes to complete. You will know it’s complete once you see the message “Finished APFS operation on identifier.” By now, your SSD should already be formatted to APFS.

To Convert or Not to Convert?

Converting your external drive to the new file system will allow you to enjoy the same benefits you get from converting your main drive, and vice versa. Copying and duplicating files will be faster. Partition management will also be better. Most importantly, native encryption will now be allowed.

There is a catch, though. If you convert a drive to APFS, it won’t be able to read other Macs or MacBooks that are not running on the same format.


Like the Mojave Installation error, there are ways to fix “Data couldn’t be read because it isn’t in the right format” error. We listed possible solutions above. Hopefully, one of the two techniques worked.

What you can do now is to be proactive against future errors. To do that, you may download and install a Mac cleaning tool that is trusted by many. As long as you use the right tool, errors won’t stand a chance.

Are you still having problems on Mojave? Drop them below and we’ll try to help you find answers in our future posts.

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