Why does the copy start and then fail instead of failing immediately?

Finder starts writing the file and only encounters the 4 GB limit when it reaches that point in the transfer. This is why the error often appears partway through a large copy.

Is exFAT a good replacement for FAT32?

For most purposes, yes. exFAT removes the 4 GB file size limit while maintaining broad compatibility with macOS, Windows and some Linux systems. It is the sensible format for an external drive shared between platforms.

Will reformatting damage my external drive?

Reformatting is a normal storage operation and does not damage the drive hardware. It erases the data on it, which is why backing up the drive's contents before reformatting is essential.

Can I get the partially copied file from the destination?

A file that was not completely written is almost certainly incomplete and unusable. Delete it from the destination and use one of the resolution steps above before retrying the copy.

Mac Error Code 0: File Transfer Troubleshooting

Symptom

Mac Error Code 0 appears in Finder when copying a file to an external drive or another storage location.

Error Code 0 most commonly appears when you try to copy a file larger than 4 GB to a drive formatted as FAT32.
FAT32 has a per-file size limit of approximately 4 GB. macOS formats a file in progress and then cannot write more.
Reformatting the drive or splitting the file often resolves the error.

What Error Code 0 actually means

Mac Error Code 0 is a general file operation failure. When it appears specifically during a copy to an external drive, it most often means the operation encountered a boundary the file system cannot cross — almost always the FAT32 file size limit.

FAT32 is an older file system format still used on many external drives, USB sticks and memory cards because it is compatible with both macOS and Windows. Its per-file size limit is 4 GB minus one byte. A video file, disk image or archive larger than that cannot be written to a FAT32 volume as a single file.

Check the format of your drive

Select the external drive in Finder
Click once on the drive in the sidebar or on the desktop to select it.
Get Info
Press Command-I. In the info panel, look at the 'Format' field. If it says MS-DOS (FAT) or FAT32, you have identified the likely cause.

Other formats

exFAT, APFS, Mac OS Extended (HFS+) and NTFS all support files larger than 4 GB. If your drive shows one of those formats, the cause of the error is something else.

Options when the drive is FAT32

You have a few approaches, depending on whether you need the drive to remain readable on Windows machines:

Reformat the drive as exFAT using Disk Utility. exFAT supports large files and works on both macOS and Windows without additional software. This erases all existing content — back up anything on the drive first.
Reformat as Mac OS Extended (HFS+) or APFS if the drive will only be used with Macs.
Split the large file into parts smaller than 4 GB before copying, if reformatting is not an option. Some archive tools can split files into a series of smaller segments.

Reformatting erases the drive

Using Disk Utility to change a drive's format removes all existing content. Copy anything important off the drive before reformatting.

Other possible causes

If the drive is not FAT32 and the error still appears, consider these other possibilities:

The destination volume is full or nearly full — check free space.
The drive is failing and encountering bad sectors — copy critical data off and check disk health via Disk Utility.
The file has a name containing characters that the destination file system cannot handle — try renaming the file to remove special characters.
The source file is damaged — try copying a different file to see if the error is file-specific.

Frequently asked questions

Sources and further reading

About file system formats — Apple Support

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Ruben Alvarez

Mac troubleshooting writer

Mac troubleshooting writer covering startup behaviour, storage, Finder problems and macOS error messages.

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