If you have just bought a USB flash drive or memory card that looks too good to be true, you usually want two different things at two different moments. First, you want a quick answer: is this drive obviously fake? Later, if the quick answer is not clear, or if the drive will hold something important, you want proof. FakeFlashTest and H2testw were built for those two different moments. FakeFlashTest is a fast screen. H2testw is a full write-and-verify test. Understanding that difference is more useful than asking which tool is “better” in the abstract, because using the wrong one wastes either your time or your certainty.
FakeFlashTest, by Steve Si of RMPrepUSB, is a freeware, portable, Windows-only tool. Its latest release, v1.1.5, is described by the developer as the latest Beta, and it must be run as Administrator or it will not list your drives. H2testw is also a Windows tool, originally written in German with an interface that can be switched to English, and it has been the long-standing reference test for fake capacity for many years. Both are free. Neither can repair a fake drive. What separates them is method, thoroughness, and time.
How each tool actually tests
The Quick Size Test in FakeFlashTest writes small 512-byte marker blocks at intervals across the drive, starting from the end of the drive and working back. That design is deliberate. A fake drive lies about its size: hacked controller firmware reports a small amount of real flash memory as a huge capacity. Writes that go past the real capacity wrap around and overwrite older data. By checking the far end first, a quick screen can often expose that lie without writing to every single sector. The trade-off is stated plainly by the developer himself: the quick test does not thoroughly test all the memory, and it does not check for faults across the whole device. It is a screen, not a certificate.
H2testw takes the opposite approach. It fills the whole available space with test files, then reads every file back and verifies it. If any part of the reported capacity is fake, the verification step will eventually meet data that was overwritten or never really stored, and the test fails. That is why H2testw is treated as the thorough reference: nothing is sampled and nothing is skipped. The cost is time. On large or slow media the write and verify cycle can take hours, and you need to plan for that rather than interrupt it halfway and wonder what the partial result meant.
| Tool | Method | Destructive? | Thoroughness | Platform | Cost |
|---|---|---|---|---|---|
| FakeFlashTest (Quick Size Test) | 512-byte marker blocks at intervals, starting from the end | Yes | Quick screen only; does not test all memory | Windows | Free (freeware) |
| FakeFlashTest (Test Empty Space) | Fills free space with test files and reads them back | Designed to preserve existing files; back up first | Broader than Quick, still a practical screen | Windows | Free (freeware) |
| H2testw | Writes test files across the whole available space, then verifies | Uses available space; back up first | Full verification of tested space | Windows | Free |
When FakeFlashTest is the right first step
Use FakeFlashTest first when you have just received a drive, you have several drives to triage, or you need a fast reason to start a return before a deadline closes. Its other mode, Test Empty Space, fills only the free space with test files and reads them back, with interval checks as it goes. That mode is designed to preserve existing files, although you should back up first anyway, because a file that already sits in a bad area can still be damaged. For a step-by-step walk-through, see our guides on how to test a USB flash drive for fake capacity and how to test a microSD card for fake capacity. You can get both tools’ context and the current FakeFlashTest build from our download page.
Speed here should be understood honestly. A quick screen is quick compared with filling an entire drive, not instant in every case. A small, fast, genuinely fake drive can fail very quickly because the end of the drive is checked early. A large drive, a slow card reader, or a drive that is mostly genuine will take longer. Do not treat any single timing you read online as a promise for your hardware. What you are buying with the quick test is triage: an early, credible signal that lets you decide what to do next.
When you still need H2testw
Run H2testw when you need certainty: when FakeFlashTest passes but the price or listing still looks suspicious, when you are gathering evidence for a dispute, when a seller asks for proof, or before you trust a drive with photos, work files, or a backup you cannot recreate. A pass on a sampled test can never prove that every block is good, and the developer of FakeFlashTest does not claim otherwise. That honesty is a strength. The honest workflow is fast screen first, full proof when it matters: screen everything with FakeFlashTest, then fully verify the drives you will actually keep and rely on.
There is also a middle situation worth naming. If H2testw reports errors, do not re-run tests hoping for a different answer, and do not keep using the drive for anything important. Data that was written past the real capacity has usually been overwritten, and overwritten data is usually unrecoverable. Follow what to do next when a fake drive is confirmed and learn to read FakeFlashTest results correctly before you file anything. If you are comparing other pairings, our FakeFlashTest vs F3 comparison and the hub of the best fake USB drive test tools show where each tool fits.
Verdict
Choose FakeFlashTest when you need a fast, destructive screen on Windows and you understand its limits. Choose H2testw when you need a thorough write-and-verify result and you can give it the hours it may need. Used in that order, the two tools do not compete; they complete each other. Screen first, prove second, and never store the only copy of anything on a drive that has only passed a spot check. That single habit will protect you from most fake-capacity losses, whichever tool you start with. Get started via the FakeFlashTest download and keep H2testw in reserve for the drives that pass the screen and earn a place in your kit.