f3write(1) test real flash memory capacity

Other Alias



f3write [--start-at=NUM] [--end-at=NUM] <PATH>
f3read [--start-at=NUM] [--end-at=NUM] <PATH>


F3 (Fight Flash Fraud or Fight Fake Flash) tests the full capacity of a flash card (flash drive, flash disk, pendrive). It writes to the card and then checks if can read it. It will assure you haven't been sold a card with a smaller capacity than stated.

When writing to flash drive, f3write fills the filesystem with 1GB files named N.h2w, where N is a number (i.e. /[0-9]+/).

WARNING: all data on the tested disk might be lost!


Initial number of file names. Default value is 1.
Final number of file names. Default value is "infinity".


To write over a flash drive mounted at /media/TEST:

      $ f3write /media/TEST
To read this flash drive:

      $ f3read /media/TEST


F3 was written by Michel Machado <[email protected]>. This manual page was first written by Joao Eriberto Mota Filho <[email protected]>.