If your files are being deleted after transferring them from a Mac to another external hard drive (HDD or SSD), this is an unusual and concerning issue that could be caused by several factors. Understanding the root cause is crucial to prevent further data loss. Here’s a breakdown of possible reasons, troubleshooting steps, and preventative measures.
Possible Causes
1. File System Incompatibility
Different operating systems and external drives use different file systems. For example, macOS commonly uses APFS or HFS+, while many external drives come pre-formatted with exFAT or NTFS (used mainly by Windows). If you transfer files from a Mac-formatted drive (APFS or HFS+) to an external drive that’s not fully compatible, the data may not be handled correctly, leading to file corruption or deletion.
2. Faulty or Corrupt External Drive
If the external hard drive is faulty, has bad sectors, or its file system is corrupted, it may delete or fail to properly store files. This can happen without obvious warning signs, especially if the drive is older or has been improperly ejected multiple times.
3. Improper Ejection or Transfer Interruptions
If the external drive is disconnected before the file transfer is complete, the files may appear to transfer but actually be incomplete or lost. macOS uses a caching system that writes data in stages, so pulling the plug too early can cause incomplete or deleted files.
4. Third-Party Software or Background Processes
Sometimes antivirus software, backup utilities (like Time Machine), or third-party file management apps interfere with file transfers. In some rare cases, they may quarantine or remove files if they are flagged as suspicious, even if they are not harmful.
5. Hidden Files or Permissions Issues
macOS can treat files differently depending on their permissions and metadata. If files are transferred without preserving these attributes, they may be hidden, unreadable, or appear deleted when accessed from another system.
Troubleshooting Steps
Check the Drive on Another Computer
Connect the external drive to a different computer and see if the files are visible. Sometimes, files may not be deleted but just hidden due to compatibility or OS differences.
Enable Hidden Files View
On macOS, press Command + Shift + . in Finder to reveal hidden files. On Windows, enable "Show hidden files" in File Explorer. Your files might still be there but not visible.
Use Disk Utility (macOS) or Disk Management (Windows)
Check the health of your external drive. Look for errors or corrupt partitions. You can run First Aid in Disk Utility on macOS to scan for problems.
Try File Recovery Software
If the files are indeed missing, recovery tools like Disk Drill (Mac), EaseUS, or Recuva (Windows) might help retrieve them—provided they haven't been overwritten.
Double-Check Eject Procedures
Always use the "Eject" function before removing any external drive. This ensures all cached data is written properly and reduces the risk of data loss.
Preventative Tips
Format Drives Properly: Use exFAT if you need to transfer files between Mac and Windows. Avoid NTFS for Mac unless you have a driver that allows full write access.
Back Up Important Data: Always keep at least one backup copy, especially when moving files between systems.
Avoid Using Old or Unreliable Drives: Drives have a lifespan; if it’s showing signs of failure (slow performance, disconnections), replace it.
Verify Transfers: After moving files, open and verify them before deleting from the source.
Conclusion
Files disappearing after being transferred from a Mac to an external hard drive is a serious issue, but often preventable. It typically stems from file system mismatches, hardware failure, or improper ejection. To minimize the risk, always verify file compatibility, back up regularly, and use reliable hardware. If files have already been lost, act quickly with recovery tools and avoid using the drive to prevent overwriting data.