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Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Stop using a drive that fails a full-capacity test for important files until you know why it failed. Copy any readable files to separate, known-good storage, save the test report, check the USB port, cable, adapter or card reader, and repeat a complete write-and-read test on an empty device. A repeatable failure—especially on a newly purchased drive—is sufficient reason to request a return or exchange. A test failure can indicate counterfeit capacity, but it can also be caused by defective memory, an unstable connection, a bad reader or file-system trouble.
Formatting may correct some file-system errors; it cannot add physical storage to a counterfeit device or reliably repair failing memory.
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What a failed fake-capacity test actually means
Tools such as H2testw and F3 do not verify a label printed on a drive. They write known test data across the available space and then read it back. A failure means that some of the data written during the test could not be returned exactly as expected.
Counterfeit flash storage is one explanation. A controller may report, for example, a large capacity while the physical memory is much smaller; once the real storage is filled, later data can overwrite earlier data or disappear. The H2testw README notes that writing beyond a fake drive’s real capacity often damages its file system and that the program does not identify the specific type of fake.
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However, the result is not proof that a seller deliberately committed fraud. A failing memory chip, damaged card, bad USB port, loose connection, unsuitable adapter, or reader problem can produce similar errors. The first objective is therefore to protect data and eliminate the test path as a source of error.
Protect data before testing again
Stop using the suspect drive for important files
Do not continue copying photos, documents, backups or application installers to a device that has failed verification. A drive that cannot preserve test data may silently corrupt ordinary files. Disconnect it after copying anything you need, and use another storage device for ongoing work.
Copy readable files to separate storage
If the drive contains files you need, copy them to a known-good disk or to two independent destinations when the files are irreplaceable. Open several copied files to confirm that they are usable. Do not move the only copy; use a copy operation so the original remains available while you assess it.
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Do not test a non-empty card
Run a destructive full-capacity test only on an empty device. F3’s usage documentation warns: Therefore, it is not wise to test nonempty cards because if the card has a problem, it may erase the old files.
Treat that warning as a practical data-protection requirement, not an optional precaution.
Record the result while it is available
Save the H2testw or F3 output, screenshots and the date of the test. Record the amount verified, the first error location, whether the error was a write or read failure, and any message about corrupted or missing data. This information helps distinguish a repeatable capacity boundary from scattered connection errors and gives a seller evidence for a return request.
Keep the purchase receipt, order number and packaging if the device is new. Do not alter the report to make it fit a conclusion: a consistent failure point is useful evidence, while a changing point may indicate an unstable connection or failing hardware.
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Check the entire connection path
Before declaring a drive counterfeit, remove the easy external causes. Disconnect and reconnect the device firmly, then perform the test from a different computer port. Avoid unpowered hubs during diagnosis. For a microSD or SD card, use another known-good reader or adapter; for a removable USB drive, try a different port and, if applicable, another cable.
Use the same test settings after changing one part of the path at a time. If the error disappears with a different reader or port, the original accessory is suspect. If the failure follows the drive across computers and readers, the drive itself becomes more likely to be at fault. These checks cannot authenticate a brand or establish a seller’s intent, but they prevent a defective test setup from sending a good drive back unnecessarily. TP-Link’s Fake SD Card Test and Verification Guide also treats the reader and connection as part of the verification process.
Run a clean, full write-and-read test
- Prepare an empty device. Copy off anything you need, then remove the remaining files. Confirm that the destination used for your backup is not the device being tested.
- Choose the test tool for your system. H2testw writes test files over the available space and verifies them. F3 provides comparable tools documented in its official usage documentation.
- Use the full available capacity. A short sample can miss a fake-capacity boundary near the end of the device. A complete test is slower on large or low-speed media, but it is the relevant test for the capacity claim.
- Let both phases finish. Writing alone is not enough. The read-back phase checks whether the stored pattern survived, which is where overwritten or corrupted data is exposed.
- Save the final report. Note the verified amount and every error location or type. Do not unplug the drive while the test is running.
- Repeat only after changing a variable. If the first run failed, reconnect through a different port or reader and perform another full test. Repeating the identical setup without changing anything adds little evidence.
A full test can take hours on a large device. Do not infer that a drive is healthy merely because an early portion passes; the untested remainder may contain the failure.
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How to read the failure pattern
| Observed result | What it suggests | Next action |
|---|---|---|
| Errors begin near a similar capacity on repeated tests, even with another port or reader | The reported capacity may exceed the usable physical memory, or the device may have a repeatable hardware failure. | Stop relying on the device and request a return or exchange, supplying the saved reports. |
| Errors move to different locations or disappear after changing the port, cable or reader | An unstable connection, adapter, reader or USB port is more plausible than a fixed capacity boundary. | Replace the faulty path component and run a complete test again. |
| Scattered read or write errors continue on multiple known-good connections | The flash memory or controller may be defective even if the capacity is genuine. | Treat the drive as unreliable and pursue replacement rather than storing important data on it. |
| The test stops because the file system becomes damaged after writing far into the device | This can occur when a controller exposes more space than the physical memory can hold; it can also follow severe hardware failure. | Do not format repeatedly in an attempt to manufacture capacity. Preserve the report and seek a return. |
| The complete test passes | The tested area stored and returned the pattern correctly during that run. | Keep backups and monitor the device; a pass is not a lifetime reliability guarantee. |
These patterns are clues, not a laboratory determination of authenticity. The test cannot identify the seller’s intent, verify a brand, or guarantee that the device will remain reliable after it passes.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why formatting is not a cure
Formatting creates or rebuilds a file system; it does not change the amount of physical flash memory. It may help when a legitimate device has a damaged directory structure or incompatible file-system configuration, but it cannot make a counterfeit controller store data beyond its real limit. It also cannot reliably repair memory that is wearing out or a controller that is failing.
If you format before preserving the report, you may destroy clues about the original failure. Only consider a format after your files are safe, the connection path has been checked, and you have a specific file-system symptom to address. Afterward, run a new full write-and-read test; a format that appears to complete successfully is not evidence that the underlying storage is sound.
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When to return or exchange the drive
Newly purchased device
A new drive that fails again at a similar point after connection checks should not be used for valuable data. Contact the seller or manufacturer through the applicable return or warranty process. Include the model and serial information, purchase details, test date, tool used, verified capacity and screenshots of the errors. Ask for a refund or replacement rather than a formatting suggestion.
Older device with no return option
Do not trust it with the only copy of anything. If you must use it temporarily for disposable transfers, keep independent backups and treat its capacity as unverified. A recurring full-test failure is a reason to retire the device, not to lower the amount of data stored until the error is avoided.
Do not rely on a capacity-setting workaround
Utilities that hide the failing portion or change a displayed capacity do not repair the memory or controller. They can make an unreliable device appear normal while leaving data at risk. Replacement is the safer resolution when a full test repeatedly fails.
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A successful complete test is meaningful evidence that the tested area accepted and returned the known pattern during that particular run. It does not replace a backup, protect against accidental deletion, or establish long-term endurance under heat, repeated writes or physical damage. Continue using a sensible backup strategy even for media that passes.
Conversely, one failed run is not enough to accuse a seller of counterfeiting. Check the computer, port, cable, reader and adapter, then repeat on an empty drive. A repeatable failure across a clean test path is the practical threshold for stopping use and pursuing a return, regardless of whether the ultimate cause is counterfeit capacity or defective genuine hardware.
A concise decision checklist
- Have all readable files been copied to separate, known-good storage?
- Is the suspect device empty before another destructive test?
- Did you save the original report, screenshots and purchase information?
- Did you try another computer port and, for a card, another reader or adapter?
- Did a complete write-and-read test fail again at a similar point?
- If the device is new, have you requested a return or exchange instead of repeatedly formatting it?
- If the test passed, are backups still in place?
If the answers show a repeatable failure, stop treating the drive as storage you can trust. Preserve the evidence and replace it.
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