With the popularity of SD cards for expanding storage on devices like cameras, phones, and laptops, fake and counterfeit cards have become more commonplace. Fortunately, there are several ways to test whether an SD card you purchased is genuine or not before trusting it with your important photos, videos, documents, and other data.
Look for signs of a fake SD card
Here are some telltale signs that an SD card may not be authentic:
- The price seems too good to be true – extremely low prices can indicate a counterfeit card
- No branding or nonsensical branding on the card and packaging
- Misspellings or grammatical errors on the card or packaging
- The packaging is different from official branding
- The card does not look quite the same as a normal SD card
- The stated capacity seems excessively large for the type of card
If you purchased an SD card online, be extra wary of exceedingly cheap cards being sold directly from China on sites like eBay or Amazon Marketplace. This is a common source for knockoff and fake cards.
Try the card in your device
The simplest test is to insert the card into a phone, camera, laptop, or other device and see if it is detected as expected. There are a few signs that could indicate the card is fake:
- The device does not detect the card at all
- The device detects the card, but shows significantly less storage capacity than advertised
- Error messages about the card being unreadable or damaged
- SD cards usually come pre-formatted, but if you need to format, formatting fails
- The card’s speed is very slow compared to expectations
- Files cannot be saved to the card or immediately become corrupted
These issues tend to come from low-quality memory chips that are faulty, unstable, or do not match the stated capacity. Even if the card seems to work at first, fake cards often fail quickly with use as data fills up unused space.
Check the physical SD card
Take a close visual inspection of the SD card itself. Signs of a fake include:
- Cheap or poor manufacturing quality like uneven seams, misaligned parts, or flimsy casing
- The contacts do not look crisp and clean
- The branding engraving looks uneven, faded, or double stamped
Of course, a fake card may look perfectly normal and high quality at a glance too. So move on to some more rigorous physical checks.
Check card weight and dimensions
Weigh the SD card on a high-precision scale like a jewelry scale that measures down to 0.1 grams. Compare this weight to legitimate specs for that card type online. Fake cards often weigh noticeably less than they should because they have fewer memory chips.
Similarly, use a caliper to precisely measure the card’s length, width, and thickness in millimeters. Fake cards may be thicker or thinner than standard specs. For example, a standard 32GB SD card should be approximately:
- Length: 24 mm
- Width: 32 mm
- Thickness: 2.1 mm
Matching the exact measurements may require some careful research since SD cards come in types like SDHC and SDXC with slightly varied sizes. Consult the manufacturer’s specifications for your specific card model if possible.
Check flexibility
Carefully try bending the SD card between your fingers. Real SD cards have some flex, but they shouldn’t bend excessively or feel flimsy. Fake cards tend to be much more flexible.
Try scratching the card
SD cards have a hard, durable plastic shell. Try gently scratching or scuffing the edge or back of the card on a rough surface like unglazed ceramic. Fake cards tend to show scratch marks much more easily while real SD cards are generally very scratch resistant.
Listen for rattling
Shake the SD card next to your ear. You shouldn’t hear anything rattling around inside. Any rattling noises likely mean cheap, loose components that can degrade performance and reliability.
Run software checks with SD tools
For the most thorough verification, use free SD card testing and benchmarking software. These will analyze technical details like the card’s file structure, storage blocks, error rates, speed, and more. Look for these tools online:
- H2testw (Windows) – Tests card capacity and performance
- F3 (Linux/Mac) – Tests for fake flash memory
- SD Card Formatter (Windows) – Checks for errors and quick formats the card
- SD Bench (Android) – Benchmarks read/write speeds
Running these tools requires inserting the SD card into a computer or phone. They will be able to detect many fake or underperforming cards by looking for issues like:
- Less usable capacity than advertised once formatted
- Read/write speed significantly slower than expected
- High unstable error rates
- Errors during the full format process
H2testw
H2testw is a commonly recommended SD card tester for Windows. To use it:
- Download and install H2testw to your Windows PC
- Insert the SD card into your computer’s card reader
- Launch H2testw and select the correct drive letter for your SD card
- Check “all available space” and click “Write + Verify”
- Wait for the full scan to run – this can take a while depending on the card size
- If the test reports errors or mismatches, the card is likely fake or defective
H2testw will fully overwrite the entire card with test data, check for errors during writes and reads, and determine if the usable capacity matches the advertised capacity. This comprehensive scanning can identify fake cards even if your device did not detect any issues before.
F3
F3 is a comparable SD card tester and “fake flash detector” available for Linux and Mac. To use F3:
- Download and install F3 on your Mac or Linux system
- Insert the SD card into your computer’s reader
- Open Terminal and run “f3write” followed by the card’s device path
- Allow the test to fully run, which can take some time
- After completion, run “f3read” to verify the test data
- F3 will report if any errors are found or if the card is identified as fake
Much like H2testw, F3 will stress test the card by filling it up completely with test data. The verify pass can detect issues with fake cards even if earlier quick tests did not.
Test card speed
In addition to testing for outright fakes, tools like F3, H2testw, and SD Bench can help identify if your card is significantly underperforming in read/write speeds compared to expectations. This is useful for determining if a card labeled as high speed, UHS, or Class 10 actually meets those claimed speeds.
An extremely slow card could indicate a fake or that a legitimate card has degraded and should be replaced.
Contact the seller
If your testing conclusively shows that an SD card you purchased is fake, contact the seller immediately. Provide details of your testing process and results. Responsible sellers will want to make things right with a refund or replacement.
Avoid further use of the card since it could fail at any time and result in data loss. Securely wipe and dispose of fake cards when possible.
Conclusion
With counterfeit memory cards becoming more prevalent both online and in-store, it is important to validate any new SD card purchase before trusting it with precious data. Carefully check for visual signs of a fake, try the card in your device, inspect physical attributes, run software tools, and reach out to the seller if necessary. Applying these tips will help you identify bogus SD cards and ensure the card you use is genuine and performs reliably.