Fake Capacity Testing Tools
No single tool is right for every drive. FakeFlashTest is the fast Windows screen; the tools below cover full verification, other platforms, and controller identification. All of them test the same lie the same way at heart: write data, read it back, and see whether it survived.
FakeFlashTest
The fastest first screen for a suspect drive on Windows. Its Quick Size Test samples blocks across the advertised capacity instead of filling the whole drive, so a fake usually shows up in minutes. Quick Size Test erases the drive; Test Empty Space is designed to preserve files. Freeware by Steve Si (RMPrepUSB), Windows only, distributed as a password-protected ZIP (password “fake”). Get it from our download page.
H2testw
The long-standing full-verification tool for Windows. It writes test files across the entire capacity and reads every one back, which is thorough but slow on large drives. Use it when you need full proof rather than a quick screen. See FakeFlashTest vs H2testw.
ValiDrive
A Windows spot-check tool from GRC that samples locations across a drive to expose fake capacity quickly. It checks sampled spots rather than every block, so treat a pass as a good sign, not a guarantee. See FakeFlashTest vs ValiDrive.
F3
Fight Flash Fraud — the cross-platform option for Mac and Linux, where FakeFlashTest cannot run. Its write/read tools fill and verify the drive, similar in spirit to a full test. See FakeFlashTest vs F3.
CheckFlash
A Windows tool that can run write/read and burn-in style checks over multiple passes. It is aimed at broader flash health checking as well as capacity problems. See FakeFlashTest vs CheckFlash.
ChipGenius
A Windows utility that reads a USB drive’s controller and flash chip information. It does not test capacity itself, but the controller details can corroborate what a capacity test found. See FakeFlashTest vs ChipGenius.
RMPrepUSB
Steve Si’s broader USB boot and formatting toolkit, which includes its own quick size test. FakeFlashTest is the focused, standalone capacity tester from the same developer. See FakeFlashTest vs RMPrepUSB Quick Size Test.