f3

A command-line tool that tests flash drives and memory cards for fake capacity and real performance.

FreeOpen sourceLinuxCommand line
Official websitegithub.com

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About f3

f3, short for Fight Flash Fraud, checks whether a USB stick or memory card really holds what its label claims. It fills the device with pseudorandom data and then reads it back to see whether the same data comes out, which exposes counterfeit drives that report more capacity than they have.

It also measures read and write performance. The project is open source and developed on GitHub, with Docker and Nix files for building.

Strengths

  • Detects fake-capacity flash drives and cards
  • Verifies data by writing and reading back pseudorandom content
  • Also reports real read and write speed

Limitations

  • Command-line only
  • A full test writes to the whole device and takes time

Details

Pricing
FreeFree and open source.
License
GPL-3.0
Developer
Michel Machado
Platforms
Linux, Command line
How it runs
Downloadable app
Account
Not required
Works offline
Yes
Best suited for
Checking a newly bought USB stick or SD card before trusting it with data
Last verified
Added
Provenance
Facts checked against the developer's own pages and store listings, 1 sources on file.

Alternatives to f3

Compare all

Software that can replace f3 for an important use case, and what changes if you switch.

  • ValiDrive

    A free GRC utility that checks whether a USB drive really holds its advertised capacity.

    FreeProprietaryWindows

    ValiDrive is a free Windows GRC utility that spot-checks USB drives for fake capacity quickly instead of writing the whole device, but it does not measure speed.

Similar software

Related functionality, not necessarily a direct replacement.

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