USB drive test for fake capacity and real speed

Three honest reasons. First, the test writes only to FREE space — existing files are never touched, and the report lists them separately ("Existing data — not tested"). Second, drive makers count in decimal gigabytes (128 GB = 128 billion bytes) while part of that is taken by the file system itself. Third, a few percent goes to formatting overhead. The report adds these up and shows the estimated total capacity, so you can see whether it matches the marketed size. For a 100% test, empty the drive first.

No — this tool does not force you to. It writes sequentially and re-reads earlier blocks while writing. The moment a fake controller wraps around or silently discards data, we catch it, stop the test, and bisect the real capacity. For a typical fake (128 GB claimed / 8 GB real) the test stops after about 8–10 GB written, which takes 1–3 minutes on USB 3.0.

To be 100% sure a drive is genuine, every byte has to actually be touched. There is no physically honest shortcut — any tool that claims "instant verification" is sampling at best and guessing at worst. Measured across real drives, expect roughly 2 minutes per GB: about an hour for 32 GB, 4–5 hours for 128 GB, and days for a multi-terabyte disk. That is why the test can be interrupted and continued: the data already written stays on the drive, and resuming picks up where it stopped instead of starting over.

Fake drives have a modified firmware that reports a larger capacity than the physical storage. A "128 GB" fake might only have 8 GB of real NAND. When you write beyond the real capacity, the controller either wraps around (overwriting earlier data), silently discards the writes, or returns zeros. Files appear to save but are corrupted when read back.

The verification principle is the same — write unique patterns, read them back. This tool adds inline spot-checking so fakes are caught during writing instead of only at the final verification pass, and a bisection probe that measures the exact real capacity of a fake. No Windows install needed.

No. The tool creates temporary test files (timbrica_test_*.bin) in the folder you select. Your existing files are not touched. Test files are automatically removed after the test.

The tool uses the File System Access API to write and read files directly on your drive. This API is currently only supported in Chromium-based browsers. Firefox and Safari do not support it yet.

Yes. The tool works with any storage device that appears as a folder in your file system — USB flash drives, SD cards, external HDDs/SSDs, and even network drives.

It means the system never mounted it, and there is nothing to test: this tool works on top of a file system, and at that moment there is none. Zero capacity in Properties, "insert a disk", a RAW file system and a missing drive letter all look alike, but their causes differ and so do their fixes. Start with a diagnosis by symptom — it works out the cause and gives you the commands for your system. If a repair brings the drive back, come here again and check how much of the memory is genuinely alive.