USB drive overwrites older files after changing cables?

You changed a cable, copied files again, and now older documents seem to be missing or replaced. A cable does not normally decide which files to overwrite, but a connection that drops during a transfer can leave a file incomplete. Duplicate names, a failing drive, or fake storage capacity can also make files appear to vanish.

First, stop writing to the drive and protect any files you can still open. The Fake USB & SD Check can help identify a drive that claims more capacity than it really has, but it writes test data and fills the drive. Do not use it until everything important is backed up and you are prepared for the drive to be erased.

Check the drive without risking more files

1. Stop copying and back up what you can. Copy readable files to your computer or a different drive, not back onto the USB drive. Before any capacity test, read about the Fake USB & SD Check: it fills the selected drive and reads the data back, so treat it as destructive and use it only after a complete backup.
2. Check whether a file was replaced or just moved. Search the drive and your computer for the file name. Compare file sizes and modified dates, and check the Recycle Bin on Windows or Trash on macOS. A copy operation can replace a file with the same name if you choose that option.
3. Reconnect only after safely ejecting. If the drive is still mounted and responsive, eject it through the operating system before unplugging it. Then try a known-good cable and a different USB port, preferably without a hub. Do not disconnect it while a transfer is in progress.
4. Check the connection before testing capacity. If the drive repeatedly disconnects or disappears, stop using it and back up what remains through a stable connection. A capacity test cannot repair a bad cable or recover files already overwritten.
5. Run a capacity check only on an empty or expendable drive. The Fake USB & SD Check works in Chrome and Edge on a computer. Run it only after backing up the whole drive and accepting that its contents may be changed.

What the result means

A file with the same name has a newer date

The file may have been replaced by a later copy, rather than erased because you changed cables. File managers commonly ask whether to replace a same-named file during copying. A sync or backup program may also update an existing file automatically. Look for an earlier copy in a backup, cloud version history, or the computer's Recycle Bin or Trash.

The file is missing or will not open after a transfer stopped

An interrupted write can leave the file incomplete, or the file system, which organizes files on the drive, may have errors. A cable or port problem is more likely if the drive disconnects during transfers. Stop copying to it, since new writes can make recovery harder. For next steps, see what to do first when recovering data from a fake drive.

Files change or disappear with one cable or port

This points toward an unstable connection, but it does not prove that the cable itself overwrote anything. A connection can fail while data is being written, and a poor contact can make the drive disconnect or reconnect. If the problem disappears with a known-good cable and direct port, replace the suspect cable and avoid using it for storage transfers.

The capacity check cannot verify all the data

The drive may have less usable capacity than its label claims, or it may have trouble writing or reading data reliably. The test can reveal a capacity or read-back problem, but it cannot tell you whether a specific old file is recoverable or identify every failing component. Do not keep using a drive that fails the check for important files.

The capacity check completes successfully

The drive stored and read back the test data during that run. That is useful evidence against counterfeit capacity, but it does not prove that the cable is sound, that every file is intact, or that the drive will remain reliable. Keep a separate backup of important files.

How to reduce the chance of losing files

1. Do not write more data to a drive with missing files. Stop copying, renaming, or formatting it. If the missing files matter, make a copy of the remaining readable data first and consider recovery before further tests.
2. Check the destination before replacing files. When copying, read the overwrite prompt carefully. Compare the source and destination names, dates, and sizes before choosing to replace anything. If the operating system offers a keep-both option, use it when you are unsure.
3. Replace a suspect cable or port. Use a short, known-good cable where applicable, connect directly to the computer, and avoid moving the cable during transfers. On a desktop, try another port; on a laptop, test a port on the computer rather than a hub or dock.
4. Safely eject the drive. Wait for copying to finish before ejecting. In Windows 11, use the USB eject option in File Explorer or the taskbar. On macOS, click the eject icon beside the drive in Finder, or drag the drive to the Trash eject symbol.
5. Check the file system only after backing up. On Windows 11, open File Explorer, right-click the drive, choose Properties › Tools › Check. On macOS, open Disk Utility, choose View › Show All Devices, select the volume, then choose First Aid. These checks can change file-system information, so do not run them first if you need to recover files.
6. Retire a drive that keeps failing. If files become unreadable across multiple known-good cables and computers, or the capacity check fails after you have backed up the drive, do not trust it with the only copy of anything. Replace it and keep the original untouched if you still need to attempt recovery.

When it is the drive, not the cable

If the same files are missing on different computers, the drive disconnects with multiple cables, or a read-back capacity test fails, the drive itself may be counterfeit or failing. A new cable can improve the connection, but it cannot restore data that has already been replaced or repair damaged flash memory. If the files are valuable, stop testing and seek data recovery help before reusing or formatting the drive.

Why the capacity test needs an empty drive

A fake-capacity drive may report more space than it can physically store. When the actual memory fills, new data can overwrite data written earlier, which can make files seem valid at first and then become damaged as the drive fills. The Fake USB & SD Check writes data and reads it back to find this problem. It is not a read-only scan of your existing files, so back up the drive first and test only when you can safely clear it.

Keep a second copy of important files on a separate device, and do not treat a successful cable swap or capacity check as a backup.