- Insert your card and (for a true capacity check) make sure it’s empty / freshly formatted.
- Select the card below and allow write access when prompted.
- Run a test. Speed is quick; the full capacity/fake check can take a while (it fills the card).
⚡ Speed test
Measure sequential write & read throughput.
🔍 Capacity & fake check
Fill the card, read it back, and detect counterfeit capacity.
How it works
Counterfeit cards are reprogrammed to report a large size to your computer while containing only a small amount of real flash. When you copy more than the real amount, the extra data silently overwrites earlier data or vanishes — so photos and videos become corrupted later, when it’s too late.
This tool uses the same idea as the open-source F3 (Fight Flash Fraud) utility: it writes files where every block is stamped with its own position, then reads everything back. On a genuine card every block returns exactly what was written. On a fake card, blocks come back with the wrong stamp — revealing the card’s real capacity.
Privacy: nothing leaves your computer. The page only touches files it creates (named memcardtest-*.mct)
and never reads your existing files.
FAQ
Which browsers work?
Chrome, Edge, Brave and Opera on desktop. Safari, Firefox and mobile browsers don’t allow writing to removable drives.
Will this erase my card?
No. It only adds its own test files and can delete them afterward. But for an accurate capacity verdict, test an empty card so there’s room to fill.
Why is it slower than a native app?
The browser adds a safety layer between the page and the drive. Speed numbers are still a good relative measure; for the last few percent of raw performance, a native tool will edge it out.
The full test is taking forever.
Filling a large card writes tens of gigabytes at the card’s (often slow) write speed. Use a smaller “How much to write” limit for a quick sanity check, or the full option overnight for a definitive result.