Step‑by‑Step H2testw Tutorial for Detecting Fake CapacityFake-capacity USB drives and SD cards are common and can cause silent data loss when they report more space than they actually have. H2testw is a lightweight, free Windows utility designed to detect these counterfeit storage devices by writing and then reading test data across the device to confirm real usable capacity. This guide walks you through everything: downloading and preparing H2testw, running thorough tests, interpreting results, and recommended next steps when a device fails.
What H2testw does (brief)
H2testw writes large test files to the target device and then reads them back to verify integrity. If the drive’s controller lies about capacity, H2testw will detect mismatches, corrupted data, or write failures. It does not repair devices — it only reports whether the medium reliably stores data.
Before you start — warnings and preparation
- Back up any important data on the device. H2testw will overwrite free space and may write to the whole device if you instruct it to.
- H2testw runs on Windows only (officially). For macOS and Linux, consider F3 (Fight Flash Fraud) which offers similar functionality.
- Testing large-capacity devices can take a long time (hours) depending on device speed and interface (USB 2.0 vs USB 3.x).
- Use a reliable USB port and avoid hubs when possible. Remove any other external storage to avoid selecting the wrong drive.
Step 1 — Download and run H2testw
- Find and download H2testw from a reputable source. The program is distributed as a small ZIP file containing an executable (no installation required).
- Extract the ZIP and double-click H2testw.exe to run it. If Windows warns about unknown publisher, confirm you want to run the file only if you downloaded it from a trustworthy site.
Step 2 — Choose language and interface basics
H2testw often opens with a language selection; pick English if you prefer. The main window offers two core actions: “Write + Verify” (the full test) and “Verify only” (useful if test files were previously written). There’s also a field to select the target drive and an option to limit the test to available free space or specify a size.
Step 3 — Select the correct target
- In the “Target” area, choose the drive letter that corresponds to your USB flash drive or SD card. Double-check — selecting your system drive will overwrite data.
- Use the “Select target” button to avoid mistakes.
Step 4 — Decide test size (free space vs custom)
- For full verification of a device’s advertised capacity, set H2testw to use the entire reported free space. This is the safest approach to detect fake over-reporting.
- If you need a quicker check, you can limit the test size (e.g., a few GB). Note: partial tests can miss fake-capacity tricks.
Step 5 — Run “Write + Verify”
- Click “Write + Verify”. H2testw will begin writing test files across the selected space. The write phase creates many files named like “h2w####.bin”.
- After writing, H2testw immediately reads those files to verify their contents. The program shows progress, transfer rates, and remaining time estimates.
- Wait patiently — interrupting the process can leave test files behind; you’ll need to delete them manually afterwards.
Step 6 — Read and interpret the results
When the test finishes, H2testw provides a report. Key things to look for:
- “No errors found” — Means the tested space reliably stored and returned data; device appears genuine for the tested portion.
- Read or write errors, mismatched data, or messages saying only a smaller capacity can be verified — These indicate the device is fake or defective. H2testw will often report the actual usable capacity it could test before errors appeared.
- The report lists which files failed and at what offset; note the “Detected total size” vs “Reported size” values.
Example result interpretations
- If H2testw reports it could only verify 8 GB on a device labeled 64 GB, the drive is fake (likely real capacity ~8 GB).
- If errors appear in the middle of the test, the drive’s controller remaps writes beyond real capacity back to earlier sectors, causing overwrites and corruption.
- If errors are occasional, the device may be failing (bad flash cells) rather than forged.
Step 7 — Clean up
After testing, H2testw leaves the test files. Delete them normally via Windows Explorer to reclaim space. If you used “Verify only”, test files need to already exist from a previous write pass.
What to do if the device fails
- Stop using the device for important data.
- Contact the seller or manufacturer for a refund or replacement — provide the H2testw report as evidence.
- If purchased from a marketplace known for counterfeit goods, consider returning it and reporting the seller.
- For critical situations, consider destroying the device to avoid future accidental use.
Alternatives and additional tools
- F3 (Fight Flash Fraud) — open-source equivalent for macOS/Linux and also available for Windows via ports.
- FakeFlashTest — another Windows tool that can quickly detect some fake drives.
- Manufacturer utilities (e.g., SD Card Association tools) — useful for health checks of genuine cards.
Tips for avoiding fake-capacity devices
- Buy from reputable retailers or official brand stores.
- Check seller reviews and product photos closely — generic packaging often signals low-quality fakes.
- Beware of prices that are too good to be true.
- Test new flash drives immediately with H2testw or F3 before use.
Troubleshooting common H2testw issues
- If H2testw cannot access the drive: run as Administrator, try a different USB port, or ensure the card reader is functional.
- If the program crashes on very large devices: limit the test size or test in smaller chunks.
- Slow speeds: Check for USB 2.0 ports, faulty cables, or that the device is fake-slow.
Summary
H2testw is a simple, reliable way to detect fake-capacity and faulty USB drives by writing and verifying data across the device. Always back up before testing, use the full-space test for accurate detection, and replace or return drives that fail verification.
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