If you have ever copied large files to external hard drives or USB flash drives in macOS, you may have encountered an unidentified error, the description of which is completely uninformative. Something like “The operation could not be completed because an unexpected error occurred (error code 0).” In today’s article I will tell you what it means, why it arises and how to deal with it.

Historically, most external hard drives and USB flash drives, if they are not sold as knowingly compatible with Mac products, use FAT or FAT32 as the file system. These systems were most widely used in ancient Windows, produced in the distant 1990s, until it was replaced by the more progressive for those times NTFS.

And the only reason that removable drives like flash drives, memory cards and other drives are still using FAT32 is its versatility, more precisely, cross-platform compatibility with macOS, Linux and Windows. In addition, on any platform, users can painlessly both read and write data on such a file system, while out of the box writing to NTFS is available only in Windows.


Unfortunately, despite the technical progress, the emergence of more modern file systems and their own moral old age, hardly anyone of the major manufacturers of drives suddenly ceases to support FAT32, setting an example for the rest. Anyway, in most cases, an unknown error with a zero code may occur due to copying large files to an external hard drive formatted in FAT32.

Read more: How to Resize Partition on a Mac?

However, do not rush to blame the Finder or macOS for all deadly sins, because, like Windows/Linux, they cannot do anything – these are the “rules of the game”: the maximum file size for a volume with FAT32 must be less than 4 GB. A flash drive can be 32 GB, but the size of each file should not exceed the previously specified limit.

Now let’s try to find a solution to the problem. For example, if you are trying to copy a large archive (ZIP, RAR, DMG), then you can unpack it and transfer it into separate files and folders of approximately the same size.

On the other hand, if you only use the drive to work with macOS, it is better to completely abandon FAT32 and format the USB flash drive/disk in the native format for the desktop operating system – HFS+. This requires:

  • Make a backup of data on another disk, since formatting will destroy all files and folders;
  • In the “Disk Utility” (in the sidebar) select the external drive;
What is “Copy Error Code 0” Means in macOS?
  • Click the “Erase” tab and in the Format drop-down menu select Mac OS Extended (journal), and below enter the Volume label;
What is “Copy Error Code 0” Means in macOS?
  • And click on the ”Erase” button.
What is “Copy Error Code 0” Means in macOS?


Unfortunately, a Windows computer without “preliminary preparation” cannot even display a list of files and folders. But this is not a hopeless case, because you can always install an application like MacDrive in Windows, teach Mac OS X to write data to NTFS, or copy content over a local network using General Access.

It’s the best time to ask questions and give us your feedback in comments.


Hi there! My Name is Vincent Lago! My goal is to share insightful reviews, guides, and manuals for people looking to know more about current solutions for Apple hardware and OS. I have years of technological background knowledge including owning a custom iMacs & PCs which was using for different types of business. And now, I want to share my experience with you.

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