Test Your USB Drive — Detect Fake Capacity & Measure Speed

A free browser-based tool to test USB flash drives for fake capacity. Many cheap drives sold online are counterfeits — a "128 GB" drive might only have 8 GB of real storage with firmware that lies about the size. This tool writes unique verification patterns across the full capacity and checks earlier blocks while writing, so counterfeit drives are detected within minutes — no software to install.

How to Test a USB Drive

Plug in your USB drive

Insert the USB flash drive into your computer and make sure it appears in your file explorer.

Click "Select Drive"

Choose the USB drive folder from the browser directory picker. Chrome or Edge 86+ required.

Start the test

The tool writes 1 MB blocks up to the drive's capacity while spot-checking earlier blocks in the background.

Early stop on fakes

If the controller lies about capacity, the test halts immediately and shows the real capacity in megabytes.

Full verification for genuine drives

When no tampering is found, every block is read back and compared. Final verdict with speed stats.

Verify USB drive capacity and expose counterfeit flash drives in your browser

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Browser Not Supported

This tool requires the File System Access API, which is only available in desktop Chrome and Edge browsers.

Chrome 86+, Edge 86+, Opera 72+ Alternatives: h2testw (Windows) | F3 (Linux/macOS)

Click the button below and choose the folder of your USB drive.

How this test works

Fake drives: detected in 1–5 minutes. The test stops as soon as counterfeit behaviour is found.

Genuine drives: the full capacity is written and verified. Takes longer, but leaves zero room for doubt (≈ 10 min per 32 GB on USB 3.0).

This test writes temporary files to your drive until it is full. Your existing files are NOT deleted, but make sure important data is backed up.

✓ Test files are automatically deleted after the test completes. ✓ The test does not damage your drive — it only creates and deletes temporary files.

Test History

Ready to start. The test writes data up to the drive's full capacity, then reads it back to verify every byte.

Drive —

Fake drives: detected in 1–5 minutes. The test stops as soon as counterfeit behaviour is found.

Genuine drives: the full capacity is written and verified. Takes longer, but leaves zero room for doubt (≈ 10 min per 32 GB on USB 3.0).

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Speed

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ETA

0 / 0

Features

Honest fake detection Early stop on counterfeit Full verification for genuine drives Read & write speed

Frequently Asked Questions

Do I really need to write the full 128 GB to detect a fake?

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 and stop the test. 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.

Why does a genuine drive test take so long?

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. For a real 128 GB drive on USB 3.0, expect around 45 minutes; on USB 2.0, several hours.

How do fake USB drives work?

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.

Is this tool the same as h2testw?

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. No Windows install needed.

Will the test delete my files?

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.

Why does it only work in Chrome and Edge?

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.

Can I test SD cards or external hard drives?

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.

💡 Want us to improve this tool just for you?

We can — and it's free! Just send us a quick message with your idea. If you'd like to discuss it in detail, leave your email and we'll get back to you. You can stay anonymous.

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Published 02 Apr 2026 Updated 21 May 2026