MicroSD cards are among the most faked storage products in the world, and microSD cards fail in exactly the same deceptive way as fake USB sticks: a small card is made to report a huge capacity, works fine for a while, then quietly corrupts your files. Whether the card is destined for a phone, a dash cam, a camera, or a handheld console, test it before you rely on it. This guide uses FakeFlashTest, the freeware Windows tool by Steve Si, to check a card properly.
FakeFlashTest is Windows-only and portable, with no install. You run it on a Windows PC even if the card will spend its life in a phone or camera. Get it via our download page, which links to the official download from the developer. If you have never tested storage before, the general workflow in our USB flash drive testing guide is worth reading first — the principles are identical, and this guide focuses on what is specific to cards and readers.
Use a proper card reader — this step decides the test
FakeFlashTest tests what Windows can see, so the card must appear in Windows as a drive with a letter. The reliable way to do that is a good USB card reader plugged directly into the computer. A reader that constantly disconnects, runs extremely slowly, or only works intermittently will produce confusing results and painfully long tests.
If you need a reader, a USB 3.0 UGREEN reader via /go/ugreen-card-reader is genuinely useful kit for this job — not an accessory for its own sake, but the piece that makes the test trustworthy. Plug the reader directly into the PC, preferably a rear port on a desktop or a main port on a laptop. Avoid USB hubs for testing: hubs add another device that can drop the connection, share power, or slow the transfer, and they make troubleshooting harder. Avoid the built-in slow card slot on some laptops for the same reason if a proper reader is available.
Insert the microSD card (in its full-size adapter if your reader needs one), confirm Windows assigns it a drive letter, and note that letter carefully. If no letter appears, open Disk Management and assign one to the card’s volume — without a letter, no testing tool can address it.
Back up, then run as administrator
If the card already holds photos or recordings, copy them off and verify the copies open before you test. One FakeFlashTest mode is destructive, and even the preserving mode cannot protect a file that already sits in a bad area of a fake card.
Extract the official ZIP — the extraction password is fake, set by the developer to reduce false blocks by Windows Defender — then right-click the program and Run as Administrator. The developer is clear: without administrator rights, FakeFlashTest will not list USB drives, and a card in a reader counts for this purpose. An empty list almost always means you skipped this step. Our dedicated guide to that symptom is linked from the troubleshooting section if you need it.
Choose between Quick Size Test and Test Empty Space
For a new, empty card — the most common case — run the Quick Size Test first. It writes and reads back 512-byte marker blocks at intervals across the card, starting from the end, so it can expose an inflated capacity without filling every byte. It is destructive: anything on the card will be lost, which is fine for a new card and exactly why you backed up an older one. The method is explained fully in our Quick Size Test guide.
If the card already holds files you must keep in place, use Test Empty Space instead. That mode writes test files only into the free space and reads them back at intervals, and it is designed to preserve existing files. Understand its limit, detailed in our Test Empty Space guide: it can only test the space that is currently free. A card that is nearly full leaves it almost nothing to check, so for a trustworthy verdict on a used card, move the files off, back them up, and run the Quick test on the empty card instead.
Dash cams, phones, and why fakes fail there first
Dash cams are where fake cards cause the most painful losses. A dash cam records continuously and overwrites its oldest footage as the card fills. On a fake card, the wrap-around point arrives far earlier than the driver expects: the card reports plenty of space, the camera keeps recording, and older — or even recent — clips are silently corrupted. The failure is usually discovered after an incident, when the one clip that mattered will not play.
Phones hide the problem differently. A phone will let you save photos and apps to a fake card for weeks, because light use stays within the small real capacity. The corruption starts once total writes pass that real limit. Testing on arrival, before the card goes into any device, avoids both scenarios. A card that fails should never be promoted to dash-cam duty on the theory that it seemed to work in the shop.
Reading the result for a card
A pass on the Quick Size Test means the sampled points across the reported capacity responded correctly — a good sign, and for most buyers enough to proceed, ideally followed by formatting the card in the device that will use it. The developer is honest that FakeFlashTest is a quick screen, not a thorough test of all memory or a check for every fault, so a pass is not a guarantee against a card failing later for other reasons.
A fail tells you the reported capacity is false and usually indicates the approximate real capacity. Screenshot the result log straight away. That screenshot is your evidence for a refund claim, and it is far more persuasive than saying the card felt faulty. Stop using the card, do not entrust it with recordings, and replace it with a genuine card from a reputable seller. If you bought a card that failed, the same evidence routine described for USB drives applies — test, document, dispute, replace.
In short: reader first, direct connection, back up, run as administrator via the tool from the download page, test while the card is empty if you can, and act on the result immediately. A microSD card costs little to test and a great deal to trust blindly.