Troubleshooting Mac File Copy Errors (Error Code -50)

If you're copying files from a Mac to an external drive (or network share) and get "The operation can't be completed because an unexpected error occurred (error code -50)", the issue is almost always the destination file system.

Common causes:

• The destination is formatted as FAT32 or exFAT and the file has extended attributes or resource forks that don't translate
• Characters in the filename that are valid on HFS+/APFS but illegal on the destination (colons, certain Unicode chars)
• File size exceeds the FAT32 4 GB limit

Solutions:

1. Reformat the destination as exFAT (if it needs to work with both Mac and Windows) or APFS/HFS+ (Mac-only)
2. Use dot_clean to strip resource forks: dot_clean /path/to/folder
3. Copy via Terminal with cp to get more descriptive error messages than Finder provides

Modern best practice: For cross-platform external drives, exFAT is the standard — it's supported natively by macOS, Windows, and Linux without size limits. NTFS works too with macOS third-party drivers, but exFAT is simpler.