USB stick overwriting older files? How to fix it

You copy a file to a USB-A memory stick and an older file disappears, changes, or will not open. It may be a normal replacement of a file with the same name, but a fake-capacity or failing stick can also corrupt older data.

First, protect anything you can still read. Then check whether the files were actually replaced and, if the stick is empty and backed up, use the Fake USB & SD Check to test its real capacity. Do not run a full-capacity test on a stick that still contains files you need.

Check the USB stick safely

1. Stop copying files to it. Before using the Fake USB & SD Check, copy any readable files to your computer or another drive. If some files are already missing, more writes could reduce the chance of recovering them. See how to back up data before testing a flash drive.
2. Check whether a file was replaced by name. Look for the missing file in the folder where you copied it. Check its name, file extension, and modified date. A file with the same name in the same folder may have replaced the earlier version.
3. Try reading the remaining files without changing them. Copy a few important files from the stick to your computer and open those copies. Do not edit or save the copies back to the stick.
4. Test the stick only after backing it up. On a computer, open the Fake USB & SD Check in Chrome or Edge. Use it only when the stick is empty or everything on it has another verified copy. The test writes data across the drive and reads it back, so it can overwrite existing files.

If important files have vanished or will not open, skip the capacity test for now. The test is for checking a drive, not recovering data. Keep the stick disconnected until you decide whether to seek recovery help.

What the result means

A file with the same name is present

This is usually a normal file replacement, not the stick choosing to overwrite old data on its own. Many operating systems ask whether to replace a file when you copy one with the same name into the same folder. If you accepted that choice, the earlier version may no longer be in that folder. Check other folders, backups, or the computer you copied the file from.

The test reports errors during its read-back

The stick did not return the test data correctly. It may have less real storage than its label claims, or its memory may be failing. A counterfeit drive can report a large capacity to the computer, then overwrite older data when writes go beyond its actual capacity. Formatting it does not give it more real storage.

The test passes, but older files still disappear

A pass means the test data could be written and read during that run. It does not prove that every file was preserved earlier, or rule out an intermittent fault. Check for duplicate filenames, safely eject the stick, and see whether the problem happens on another computer. For more context, read why fake drives can overwrite data without warning.

The stick disconnects or shows read errors

Repeated disconnects, slow or stalled copies, and files that become unreadable can point to a damaged connector, failing memory, or a problem with the USB port. Do not keep testing a stick that contains the only copy of important data.

How to fix it

1. Use a different filename or folder. When copying files, compare the names before accepting a replace prompt. Keep separate versions in folders with clear names, or add a date to each filename.
2. Copy files off the stick, then eject it properly. Wait for copying to finish before disconnecting. In Windows 11, use the Safely Remove Hardware and Eject Media option in the taskbar. On macOS, click the eject symbol beside the drive in Finder before unplugging it.
3. Try another USB port and computer. Plug the stick directly into a USB-A port instead of a hub or adapter. If the problem happens only on one computer, check that computer's USB port and file-copy behavior. USB-A describes the connector shape, not the quality or true capacity of the storage inside.
4. Check the file system after copying your data elsewhere. On Windows 11, open File Explorer, right-click the drive, choose Properties › Tools › Check, and follow the prompts. On macOS, open Applications › Utilities › Disk Utility, select the USB drive, then choose First Aid. Repair tools can change disk data, so do not run them before copying files you need.
5. Retest only an empty stick. After you have verified a backup, run the Fake USB & SD Check. If it reports a capacity or read-back failure, do not trust the stick for important files. Formatting is not a reliable fix for counterfeit capacity.
6. Replace a stick that keeps failing. If the drive errors on more than one computer, disconnects, or fails its read-back test, move your files to a reliable replacement. Avoid using it as the only copy of anything important.

When the stick may be failing

A drive that repeatedly corrupts files, vanishes during a copy, or fails a read-back test is not dependable. If its files matter, stop using it and get advice from a data recovery service before trying repairs. If you have another copy, replace the stick rather than relying on it again. For a drive that has already lost files, start with these steps for fake drive data recovery.

Why the capacity test needs an empty drive

The Fake USB & SD Check verifies storage by filling the selected drive with test data and reading that data back. That is how it can reveal whether the reported capacity is real, but the process can overwrite files already on the stick. Use it only after backing up the contents and confirming that the backup opens. The test works in Chrome and Edge on a computer; other browsers may offer reduced access or no access to the drive.