It’s easy to forget that some technology no-nos that you’ve known about for years aren’t necessarily public knowledge. When I came across this thread on XDA, I thought it was time to remind everyone about one of the basic rules of buying flash memory: Be extremely careful about where you buy flash memory from.

Fake flash memory is a major problem. By “fake, I’m referring to several different potential problems. Cheap no-brand memory being sold as brand name memory is very common, and often very hard to spot since the memory might have the appropriate capacity and work “well.” Fast memory is more expensive than slow memory, so a noname 16GB class 2 card being sold as a SanDisk 16GB class 10 card (the class rating refers to minimum read/write speed in MB) has potential for profit, while at the same time being very hard to discover as fake if you don’t pay attention to write speeds, or assign the blame to e.g. the device hardware. The same goes for quality, where cheap memory often goes bad quickly, resulting in file corruption.

Another common, and frankly more serious, type of scam is when flash memory doesn’t have the capacity that is listed. A memory card might say 32GB, and even show up as 32GB on a device, but might actually be a lower capacity card. These cards can be hard to spot if you don’t run tools designed to find the real capacity, as they will be able to store as much data on them as the actual capacity is. If a 16GB card is being made to think it’s a 32GB card, you’ll be able to fill it up half ways before you discover something’s wrong. Many people buy high capacity cards for future use, and don’t fill it up right away. As an example, someone buys a 32GB card that’s really a 16GB card, puts it in their device, and use it without issue for a long time simply because they haven’t tried to see if it can actually store more than 16GB.

The problem of fake memory of various types is so huge that there’s really only one solution to the problem: Never, ever, buy flash memory from any source that you don’t explicitly trust. Most of these cards originate from China, and as such you shouldn’t ever buy memory directly from there. Even more local sellers might be selling fake memory, perhaps without even knowing so, having found a “great deal” on a bulk package of memory cards and decided to resell them to make a buck. The only places you can really trust are well known online stores and physical stores. In that definition are sites like Amazon.com, but not necessarily sellers that sell through Amazon.

If you for some reason have to buy from places like eBay, perhaps in order to get your hands on high capacity cards in certain countries, make sure that the price makes sense. 64GB SanDisk Ultra cards that cost $80 on Amazon don’t cost $17 anywhere else. They really don’t. 32GB class 4 cards (or worse) with a fake partition, on the other hand – now that I can see going for $17. People receiving it should have just enough time to be happy that it’s working to leave a positive rating. Then they try to write their 17th or 33rd GB of data.

This is also why the feedback rating of the seller shouldn’t be trusted in these cases, as a lot of fake flash memory never gets found out or gets found out too late to warn anyone. It’s quite easy to rack of a positive score of several hundred by the time people catch onto what’s really going on, and then all that’s needed is to delete the account and start a new one. Alternatively, drowning 100 negative comments about memory cards in 100,000 positive comments about cheap screen protectors and USB cables isn’t hard either. Think PayPal has your back? If you’re lucky, but everything has a time limit, and the question is how much effort you’re willing to spend to get back $17. Time is money after all.

To find out more about fake memory and how to check the real capacity of a chip, check out this site.