How to check storage authenticity before a backup

A new USB drive or SD card may look like a bargain, but its label does not prove it can store the amount it claims. A counterfeit drive can report a large capacity while saving new files over older ones once its real storage fills up. That can quietly ruin a business backup.

Test the drive before copying important records to it. The Fake USB & SD Check fills the storage with test data and reads it back to find its usable capacity. It checks capacity, not the manufacturer's identity or the drive's future reliability.

Check the drive's real capacity

1. Use a computer with Chrome or Edge and open the Fake USB & SD Check. This tool works in Chrome and Edge on a computer. Support is reduced or unavailable in other browsers.
2. Make a separate copy of anything on the USB drive or SD card that you need to keep. The test writes data across the storage, so use an empty drive. Do not test a drive containing the only copy of business files.
3. Connect the device directly to the computer when possible. If you are testing an SD card, insert it into a card reader. If the browser asks you to choose or grant access to a device, select the drive you intend to test.
4. Start the capacity check and let it finish writing and reading the test data. A large drive can take a while. Keep the computer awake, and do not unplug the drive or close the browser during the test.
5. Compare the usable capacity the test verifies with the capacity printed on the package. If the test reports less space than claimed or has read errors, do not use the device for your only business backup.

Capacity labels and operating systems do not always use the same units. Manufacturers usually count a terabyte as 1,000,000,000,000 bytes. A computer may display that as about 931 GB because it counts in binary units but labels them as gigabytes. A difference like that can be normal. A device that verifies only a small fraction of its advertised size is not.

What the result means

The verified capacity is close to the label

The drive stored and returned test data across nearly all of the space it claimed. That is good evidence that its usable capacity is real. It does not prove that the brand or seller is genuine, or that the device will keep working. Counterfeit devices can also have a smaller real capacity that matches the test's result but not the printed label.

The verified capacity is much smaller than claimed

Treat the device as unreliable. Some counterfeit drives change their reported capacity so the computer appears to have more room than the hardware actually provides. When that real space fills, later writes may overwrite earlier files or fail. Do not put the drive into a backup rotation based on its label.

The test reports read errors or stops unexpectedly

This can point to bad storage, but it can also come from a loose connection, a faulty card reader, or a USB hub. Try a direct port or a different known-good reader once, then retest the empty device. Repeated errors mean you should not trust it with business data.

The capacity looks right, but the drive is slow

A capacity check is not a speed test. A genuine device can still be slow, especially through an older port or reader. If slow transfers are the main concern, check the reader, cable, and port separately before deciding the storage itself is faulty.

What to do before using a questionable drive

1. Keep the original files safe. Copy anything important to another location before testing, formatting, or troubleshooting. A capacity check writes test data, so do not run it on a drive with files you cannot replace.
2. Confirm which device you selected. Check the drive's displayed capacity and name in the computer before giving the browser access. On Windows 11, use File Explorer › This PC. On macOS, select the device in Finder. Take care not to test another attached drive.
3. Use a supported browser on a computer. Run the check in Chrome or Edge on a desktop or laptop. If you used another browser or a phone, repeat it on a supported computer rather than treating an incomplete result as a failed drive.
4. Remove connection problems. Plug the drive into another computer port and avoid a hub or adapter for the repeat test. For an SD card, try a different reader. If the result changes substantially between connections, investigate the reader or connection before trusting either result.
5. Do not try to fix a capacity mismatch by formatting. Formatting changes how storage is organized, but it cannot add missing storage chips or make a counterfeit device hold its label capacity. See why formatting cannot fix fake USB capacity.
6. Return or replace a drive that fails again. Save the receipt, packaging, and test result if you need to contact the seller. Do not use a device with a repeated capacity mismatch or read errors for backups, even if it sometimes appears to work.

When the drive itself is not trustworthy

If the same capacity mismatch or read errors happen in a second reader or computer, stop using the drive for important files. A browser test cannot identify the seller or authenticate a brand, but repeated failures are enough reason to return the device or replace it with storage from a seller you trust. If you already copied files to it, compare those files with the originals before deleting the originals.

Passing a capacity test is not the same as having a safe backup

A successful result checks that the drive can store and read back data over the space it reports at the time of the test. It does not test every aspect of long-term reliability, protect against accidental deletion, or prove that your backup can be restored. Keep more than one copy of important business files, and periodically open a sample of backed-up files from each copy.

The test writes data to the selected storage on your device, and the browser needs permission to access it. Use a blank drive and make sure you have another copy of anything you need before starting.