FakeFlashTest and CheckFlash both run on Windows and both hunt for fake flash media, but they ask different questions. FakeFlashTest asks, first and fastest: does this drive have anything like the capacity it claims? CheckFlash, also written ChkFlsh, by Misha Cherkasoff, runs read and write test cycles across the drive, can show speed, and can display a drive map, which makes it a full-test tool concerned with the surface as a whole. A useful way to keep them straight is: screen for the lie, then test the surface. Screen first for the capacity lie, then, if needed, test the whole surface properly.
FakeFlashTest, by Steve Si of RMPrepUSB, is freeware, portable, and latest v1.1.5 is the developer’s latest Beta. It must be run as Administrator. CheckFlash is Windows freeware in the full-test family, alongside tools such as H2testw and F3. Both are free. The fraud they target is identical: hacked controller firmware that reports a small amount of real NAND flash as a huge capacity, so that writes past the real limit wrap around and silently overwrite older data. Directory listings keep looking normal long after the files themselves are ruined, which is why a real test, not a file copy you eyeball, is essential.
How each test spends your time
The Quick Size Test writes 512-byte marker blocks at intervals, beginning at the end of the drive. That ordering is the whole trick: the end of a fake drive’s claimed capacity is fiction, so checking there early can expose the fraud without writing everywhere. The developer’s own limit applies in full: the quick test does not thoroughly test all the memory and does not check for faults. FakeFlashTest’s Test Empty Space mode is broader, filling free space with test files and reading them back at intervals, designed to preserve existing files, with a backup still advised before you start.
CheckFlash spends your time the other way. Read and write cycles across the drive take as long as the drive takes, and on large or slow media that can be a long session. What you get in return is coverage and a visual sense of the drive: the speed information and drive map help you see the test as a picture of the device rather than a single pass-or-fail line. That does not make its verdict magic; it makes it thorough in the same practical sense as other full tests. If the cycles uncover errors, the drive has failed a test that actually visited the areas in question, which is stronger evidence than a sampled pass and sobering evidence for a refund claim.
| Tool | Method | Destructive? | Thoroughness | Platform | Cost |
|---|---|---|---|---|---|
| FakeFlashTest (Quick) | Marker blocks at intervals from the end | Yes | Quick screen; not all memory tested | Windows | Free (freeware) |
| CheckFlash (ChkFlsh) | Read/write test cycles, speed display and drive map | Write cycles; back up first | Full-test family | Windows | Free (freeware) |
A sensible order to run them in
Start with FakeFlashTest on any empty or backed-up drive. If the quick screen fails, you already have your answer for shopping purposes: the drive is not what it claims to be, and there is little value in spending hours characterising exactly how bad it is unless you need fuller evidence for a dispute. Preserve the result, read how to read FakeFlashTest results, and move to what to do next when a fake drive is confirmed. If the screen passes and the drive will hold anything important, graduate to a full test, CheckFlash or H2testw on Windows, before you rely on it. Our download page and the step-by-step guide to how to test a USB flash drive for fake capacity cover the first stage in detail.
There is one exception to that order. If a drive already contains files and has not been backed up, do not start with a destructive quick test. Back the files up first if the drive will still let you, because a fake drive overwrites its own contents as it fills, and overwritten data is usually unrecoverable. Only once a copy exists elsewhere does the destructive screen become a cost-free diagnostic. The same caution applies to any write-cycle test: testing a failing drive is safe for your verdict, not for the only copy of your data.
Limits to keep in mind
Neither tool can fix a fake drive, recover overwritten files, or guarantee that a passing drive will never develop faults later. A full test is a statement about the drive as tested, on that day, through that reader. A quick screen is a narrower statement still. Confusing those scopes is how people end up storing wedding photos on a drive that only ever passed a spot check. Compare the other pairings in this series, including FakeFlashTest vs H2testw and FakeFlashTest vs ValiDrive, or start from the hub of best fake USB drive test tools if you are choosing from scratch, including for microSD cards, which fail in exactly the same way.
Verdict
Use FakeFlashTest when you want the fastest honest answer to the capacity question on Windows. Use CheckFlash when you want full read and write cycles, a speed view, and a drive map, and you can give the test the time a full surface pass needs. Used in sequence, they are complementary: a quick screen that respects its limits, followed by a full test for anything you plan to keep. That order saves hours on obvious fakes without ever pretending that a screen is a proof. Begin with the FakeFlashTest download, and promote the survivors to a full test before they earn your trust.