Cheap 1TB flash drive: how to verify its size

A bargain 1TB flash drive can look normal in your computer, even if it cannot really store 1TB. Some drives report a made-up capacity, then overwrite earlier files when you save more data than they can hold.

To check the actual capacity, you need to write data across the drive and read it back. TooLab's Fake USB & SD Check does this in your browser. The test writes to the drive, so back up anything you need before you start.

Check the flash drive's real capacity

1. Open the Fake USB & SD Check in Chrome or Edge on a computer. This tool needs a supported desktop browser, not a phone browser.
2. Copy any files you want to keep to another location. Use a drive with plenty of free space, ideally an otherwise empty one, so the test can check as much of its capacity as possible.
3. Connect the flash drive directly to the computer. Follow the tool's prompts to select the drive and allow browser access if asked. Check the drive name carefully before continuing.
4. Start the test and leave the drive connected until it finishes. The tool writes test data and reads it back. A full-capacity check can take a while, especially on a slow drive.
5. Use the verified capacity reported by the test, not only the size printed on the packaging or shown in File Explorer or Finder. If the test stops before completion, the result is not a full check.

Do not remove the drive while the test is running. Interrupting a write or read can leave the check incomplete, and unplugging a drive during other file activity can also damage files.

What the result means

The check verifies close to the expected capacity

A drive sold as 1TB should provide close to 1,000,000,000,000 bytes before file-system overhead. Computers may display that as about 931 GiB, or label the displayed number differently. That difference is normal: drive makers and operating systems do not always use the same unit calculation.

If the test writes and reads the available capacity successfully, the drive passed this capacity check. It does not prove that the drive will keep data safely for years or that its speed matches the label.

The check finds much less space than expected

The drive may be counterfeit, damaged, or misreported by its controller. A suspicious result is not explained by the normal 1TB versus 931 GiB unit difference. Do not trust it with important files. Keep the test result and purchase details if you plan to ask the seller for a refund.

The check reports read or write errors

The drive did not reliably store and return the test data. A bad USB port or connection can sometimes cause errors, but a drive that fails again in another port or computer should be treated as unreliable, even if it appears to have the right capacity.

The test stops or cannot access the drive

This does not confirm that the drive is fake. The browser may not support the required drive access, the computer may not have granted permission, or another app may be using the drive. Fix the access problem and run a complete check before drawing a conclusion.

How to fix problems during the check

1. Use Chrome or Edge on a computer. Fake USB & SD Check works in these browsers on a computer. If you opened the page in another browser or on a phone, switch to a supported setup.
2. Allow access to the correct drive. Follow the browser prompt and select the flash drive, not another connected storage device. If you denied access, reload the page and try again.
3. Make room for the test data. Back up files elsewhere and use a drive with ample free space. A check limited to only a small amount of free space may not uncover a drive that lies about its total size.
4. Reconnect the drive directly. Try another USB port and avoid a hub or extension cable for the test. If the connection drops, the browser may not be able to finish writing and reading data.
5. Close apps that use the drive. Close any file manager window or program that may be copying, scanning, or editing files on it. Then restart the check.
6. Try another computer. If the test cannot access the drive or fails in one port, repeat it on a second computer with Chrome or Edge. A failure that follows the drive is stronger evidence of a drive problem.

When to return the drive

If a complete test confirms far less capacity than the seller advertised, or the drive repeatedly fails its read-back check, stop using it for anything you need to keep. Contact the seller for a refund or replacement. Do not try to make the drive's reported capacity match the test by repartitioning it. That changes how the space is presented, but it cannot add real storage.

What this test does not prove

A successful capacity check confirms that the tested data could be written and read back at that time. It does not measure how fast the drive will be for everyday file copies, and it cannot guarantee future reliability. For a new drive, keep a separate backup of important files even after it passes.

The test runs in your browser and works with the drive connected to your computer. Test data is written to and read from the drive, not uploaded to TooLab.