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Test whether an SD card or USB stick is fake

Fake cards claim 128 GB or more but hold far less, and quietly lose anything saved past the real size. Fake Card Tester fills the card's free space, reads it all back, and tells you how much really works and how fast.

Download for Mac Download for Windows How it works

Free in AMWT Desktop · macOS 13 or later · Windows 10 and 11 (early access)

Coming in the next version of AMWT Desktop. The download today is version 1.0.0, which has Data Recovery; it updates itself when the new version is out.

A Fake Card Tester result: the card is fake, only about 7.8 GB of the 128 GB it claims works, with a chart of where the space goes and its write and read speeds.

Fake Card Tester

What it does

  • Real capacityEvery block it writes says where it belongs, so a card that wraps round or drops data is caught, and you see how much really works.
  • Real speedAverage write and read speed over the whole card, with what that is good enough for (HD video, 4K, burst photos).
  • Your files left aloneIt only uses free space, in its own folder, and deletes its test files when it finishes or is stopped.

How it works

Fake Card Tester in three steps

  1. Choose the card

    Any card or USB stick that is mounted. No administrator password is needed.

  2. Let it write, then reconnect

    It fills the free space, then asks you to take the card out and put it back, so the check reads the card and not the computer's memory.

  3. Read the result

    Genuine, fake, or failing, with the real capacity and speeds. The test files are deleted.

Good to know

What it can and can't do

  • Only free space is tested. A full card checks little: copy its files off and empty it for a full test.
  • Filling a large slow card takes time: a 128 GB card at 20 MB/s takes nearly two hours to write.
  • If you skip the reconnect step, the result is less certain, because some of the read-back can come from the computer's memory.

Questions

Questions about Fake Card Tester

How do I check if an SD card is fake?
Fill it with test data and read it back. A genuine card returns every byte. A fake one returns errors or old data past its real size. Fake Card Tester does this for you and gives the real capacity.
Will testing delete my photos?
No. It writes only into free space, in a folder of its own, and removes its test files afterwards. Your files are not read or changed.
Why do I have to unplug the card?
Computers keep recently written data in memory. Reconnecting the card makes sure the check reads from the card itself.
What should I do with a fake card?
Stop using it for anything you care about and ask the seller for a refund. Data saved past its real size is lost.
Is it free?
Yes. Fake Card Tester is free in AMWT Desktop.

Is my SD card fake?