A capacity test that seems to hang tests your patience before it tests the drive — but a stuck test is information, not just delay. FakeFlashTest’s Quick Size Test and Test Empty Space can legitimately take a long time in several common situations, and each cause points to a different response. This guide works through what a long or apparently frozen test usually means, stated honestly and qualitatively, so you can tell patience from a genuine problem.
For how the tests are supposed to run, see our Quick Size Test guide and the main routine in how to test a USB flash drive for fake capacity. The tool itself is available via the download page. Before assuming a hang, confirm the test was started correctly: drive connected directly, FakeFlashTest running as administrator (required, or drives are not listed properly), and the correct letter selected.
First, give it a fair chance: some tests are simply slow
The developer’s famous 27-second example involved a small fake drive, and it has set unrealistic expectations ever since. That was one small device; it was never a promise. A drive reporting a very large capacity gives the test a lot of ground to sample, and the sampling is done at the speed of the slowest link in the chain — the drive or card itself, the reader, and the port. A large claimed capacity moving through a slow interface can stretch a Quick test from seconds into a long wait, and Test Empty Space, which fills real space with real files, takes longer still by design.
Judge by progress, not by the clock. If numbers, percentages, or written amounts are advancing — however slowly — the test is working. Note the current progress value, check again after a real interval, and compare. Only a test whose progress has not moved at all across a long, patient interval deserves the word stuck. Interrupting a slow-but-moving test at minute ten teaches you nothing and costs you the whole run; many “hangs” are simply big drives being big.
Slow readers and laptop slots: the bottleneck may not be the drive
For SD and microSD cards especially, the reader is frequently the slowest component. Inexpensive readers and some built-in laptop card slots move data at a fraction of what a decent USB 3.0 reader achieves, and a test that would be brisk through a proper reader can crawl through a laptop slot. The same applies to USB hubs sharing bandwidth and power, and to front-panel ports with poor connections.
The practical response is to change the rig once, cleanly, rather than repeatedly restarting the test: move the card to a proper reader plugged directly into a main or rear port, close other programs hammering the same storage, and run the test again from the beginning. Our card guide, how to test a microSD card for fake capacity, treats the reader as part of the test setup for exactly this reason. If the same drive tests briskly in a better rig, you have found your hang — and it was never the drive.
When the drive itself struggles: controllers under sustained writes
There is a more meaningful cause, and it concerns fakes directly. A fake drive’s hacked controller manages a fiction under light use, but a capacity test subjects it to sustained writes across its whole claimed range — including addresses with no real storage behind them. Under that load, cheap controllers can slow to a crawl, stutter, disconnect, or crash outright. A test that progresses normally at first and then degrades badly around a particular region is behaving consistently with having reached the end of the real chip: everything beyond that point is the controller improvising.
Heat adds to this. Small sticks and cards under sustained writing can get warm and throttle, and a device crammed against other hot hardware or used on a soft surface that insulates it will fare worse. Let the device cool, give it air, use a short extension or a rear port to move it away from heat sources if it runs hot, and retry when cool — not as folklore, but because sustained-write performance on cheap flash genuinely degrades with temperature.
What to do if it truly never finishes
If progress has genuinely not moved across a long interval — and you have confirmed the rig is not the bottleneck — stop the test cleanly where you can, safely remove the device, let it cool completely, and retry once on a different port or computer if one is available. A device that repeatedly stalls a test at roughly the same region, on different setups, is giving you a repeatable result even without a formal log line: it cannot handle sustained writes across its claimed capacity, which is precisely the behaviour of a fake or a failing device. Screenshot whatever the tool shows, note the reported capacity and where it stalled, and treat the drive as untrusted.
Do not keep a drive in service because its test “never quite finished, so it never quite failed.” An unfinished test on a bargain high-capacity drive is not a pass; it is an unanswered question with worrying body language. Either obtain a completed verdict — better rig, cooled device, clean rerun with the tool from the download page — or replace the drive through a genuine channel. And if the unfinished business is a drive that now will not format or has vanished entirely, those are separate symptoms with their own guides, linked from our troubleshooting family. Patience first, rig second, verdict third: that order resolves almost every “stuck” test honestly.