f3 is a command-line tool that tests flash storage devices to verify their actual capacity and performance against manufacturer claims and detect counterfeit or degraded storage media.
The tool addresses the problem of fraudulent flash storage by writing pseudorandom data to a device and then reading it back to verify integrity. f3write fills the device with test data while f3read checks that the written files are returned exactly as stored. The tool also includes f3fix, which creates a partition matching the actual usable size of a device that reports false capacity.
The tool suits anyone who has purchased flash storage and wants to verify it is genuine and performs as advertised, particularly useful for detecting counterfeit USB drives, SD cards, and other flash media. f3write and f3read work on mounted filesystems and are available on Linux, FreeBSD, Windows via Cygwin, and macOS. f3probe and f3fix are designed for Linux but can be run on Windows through Docker. The project positions itself as a straightforward alternative to more complex testing approaches by focusing specifically on capacity and performance verification through a simple write-and-verify methodology.
The project maintains a stable release cycle with tagged versions available for download. Development activity shows ongoing maintenance with support across multiple operating systems and compilation environments. The tool is written in C and compiles with standard build tools, with platform-specific instructions documented for Linux, FreeBSD, Cygwin, and macOS. Documentation is maintained at a dedicated site separate from the repository, indicating sustained attention to user guidance.
