I saw this method for testing micro sd cards on an Amazon review while searching for Micro SD cards. I think it’s useful and have copied it here for others to see in case the original is removed.
You will most likely get a genuine card, but there are many fakes so its essential you test your card when you receive it. Some fakes will still pass some of the test programmes.
Test with ChkFlsh, Crystal Disk Mark & the main one H2testW. H2testW tests the full capacity of the Micro SD card and will report if any are using aliasing to fake larger than real capacity. A card with it’s indicated capacity but high error rate/slow write speed indicates a ‘ghost run’. Ghost run SD cards are fake and won’t last very long.
Good results are:
A 32GB card should have a formatted capacity of around 30GB, format in FAT/FAT32 only (NTFS shortens life of flash media & wont improve performance). Warning from Nerdr – Fat and FAT32 have a file size limit of around 4GB. Do not use FAT or FAT32, just stick with NTFS, it’s worth the shorter life.
A class 10 card must have a write speed of 10MB/s minimum (large files) the first result in Crystal Disk Mark should indicate that. Cards are now appearing with the UHS-I class (marked with a 1 inside a U) these have higher clock rates so higher performance and are at least class 6 speed.
Read speeds should be over 12MB/s and getting toward 48MB/s with these.
If your memory cards speed test comes just below spec, that’s a fail, don’t assume ‘close enough’. SDHC cards have a maximum capacity of 32GB and SDXC a maximum capacity of 2TB but check your device is compatible with SDXC before choosing those over these SDHC cards.
That’s the end of the Pro tip for testing your memory cards when you get new memory for your camera, phone or other device.