Why Files deleting after transfer from mac and other external HD

Transferring files between a Mac and an external hard drive should be a straightforward process. However, in some cases, users encounter a frustrating issue where files appear to delete or go missing after the transfer. Understanding the possible reasons behind this can help prevent data loss and ensure safe file management.

1. Drive Format Incompatibility

One of the most common causes is file system incompatibility between macOS and the external hard drive. macOS uses APFS or Mac OS Extended (Journaled) file systems, while many external drives come pre-formatted as exFAT or NTFS (Windows-based systems).

NTFS drives are read-only on macOS by default. If you try to write or transfer files, the system might appear to do it, but the changes may not persist.

exFAT supports both macOS and Windows, but data corruption is more common on exFAT when improperly ejected or used across systems.

Solution: Format the drive to exFAT for cross-platform use, or Mac OS Extended (Journaled) or APFS if it's only for use with Mac. Back up data first, as formatting erases all contents.

2. File Transfer Errors or Interruptions

If a file transfer is interrupted—due to power loss, cable disconnection, or system crash—files may appear to transfer but may not be saved correctly. This can sometimes cause partial or missing files that vanish after the operation.

Solution:

Ensure the cable and USB port are functioning correctly.

Always eject drives properly to prevent data corruption.

Avoid multitasking during large file transfers.

3. Misunderstanding “Move” vs. “Copy”

When dragging files between drives, macOS may either copy or move them depending on how the action is performed. Holding the Command key during a drag-and-drop move can result in files being moved (i.e., deleted from the source) rather than copied.

If something goes wrong during this move, and the destination drive doesn't store the data properly, the file may be lost from both locations.

Solution:

Use Copy-Paste instead of drag-and-drop for better control.

Confirm that files exist on the destination drive before deleting them from the source.

4. Hidden Files or System Permissions

macOS might transfer files but mark them as hidden due to permission issues. Sometimes, you might think the files are deleted when they are simply hidden or unreadable.

Solution:

Use Finder > View > Show Hidden Files (press Command + Shift + .).

Use Disk Utility or Get Info to check file permissions.

Run First Aid on the drive using Disk Utility.

5. Antivirus or Cleanup Software

Third-party antivirus or disk cleanup tools can automatically remove files they detect as duplicates, temporary, or suspicious. If these tools are active during the transfer, they might delete files without warning.

Solution:

Temporarily disable such tools during file transfer.

Review software settings to prevent automatic deletions.

Preventive Tips

Always verify file integrity after transfer.

Back up critical files in multiple locations (e.g., Time Machine, cloud, secondary drive).

Keep external drives properly ejected and avoid disconnecting during transfers.

Keep macOS and external drive firmware/software updated.

If files are lost during transfer, tools like Disk Drill, PhotoRec, or EaseUS Data Recovery may help recover deleted or corrupted files.

In summary, file deletion after transfer from a Mac to an external hard drive can stem from file system mismatches, transfer errors, or user actions. By understanding the risks and using safe practices, you can minimize data loss and ensure reliable transfers.