Hi, I found the answer to my question in my previous topic: https://www.wilderssecurity.com/showthread.php?p=1695421 I put it to the test. I expected one of three possibilities: Everything is recoverable. Nothing is recoverable. For every block of 4K there will be 2 or 4 bytes lost. This is what I tried: I format my USB stick. (1003.5 MB free). I make a file of 1000 MB on my hard disk with random numbers of 4 bytes. I copy it to the stick. I format the stick again. I make a new file on the stick, open it, set its length to 1000 MB and close it. I copy that file to my hard disk. Then I tried several times to choose a number somewhere in one file and search that number in the other file. I tried that with both files. Whatever number I chose, I didn't find it. So if it's possible to find a number from one file in the other, then the chance is very small. So after formatting my stick all data is probably completely unrecoverable. But this isn't necessarily the same for all USB sticks. That should depend on the controller chip.