Why does this only happen with external drives?

External drives often use FAT32/exFAT which have stricter file name limits and are more prone to metadata corruption than APFS/HFS+.

Can I use Terminal instead of Finder?

Yes, cp or rsync in Terminal often succeeds where Finder fails because they handle metadata differently.

Mac Error -36 — Finder Cannot Complete Operation (I/O Error)

Warningfinder

Overview

Mac error -36 is an I/O error that occurs when Finder cannot read or write files during copy operations, typically caused by .DS_Store corruption or disk issues.

Key Details

Error -36 maps to ioErr — a general input/output error at the file system level
Most commonly appears when copying files to/from external drives, SD cards, or network shares
Hidden .DS_Store files with corrupted metadata often trigger this error
FAT32/exFAT formatted drives are more susceptible to this error
The error interrupts the copy operation, leaving some files uncopied

Common Causes

Corrupted .DS_Store files on the source or destination volume
Bad sectors or I/O errors on the storage device
Incompatible file names (special characters, very long names) for the destination file system
SD card or USB drive with write errors or failing flash memory
Network share timeout during file transfer

Steps

1Delete .DS_Store files: open Terminal and run dot_clean /Volumes/YourDrive
2Alternatively use Terminal to copy: cp -v /source/file /destination/ (bypasses Finder)
3Run First Aid on the disk: Disk Utility > select volume > First Aid
4For SD cards: copy to local drive first, then to destination
5Reformat the external drive if errors persist (backup data first)