What Is H-Testing for USB Drives. Is H2 and H5 The Same?

So What Is H-Testing for USB Drives, Really?

I’m at a wine tasting. The kind where nobody is actually tasting anything. Everyone’s holding a glass, nodding politely, and trying to look like they belong in the room.

I bump into a tech mogul. Big CEO energy. Knows markets, valuations, and boardrooms — not flash controllers.

Somewhere between the Pinot Noir and whatever someone insists is “very exclusive,” he says:

“We once had an issue with fake USB drives. Someone mentioned H-testing. What is that, exactly?”

This is where most explanations go sideways. People either oversell it like it’s some kind of security certification, or undersell it like it’s just a quick format.

So I take a sip and say:

“Okay… imagine you bought a wine cellar that claims it holds 1,000 bottles.”

Now I’ve got his attention.

Why H-Testing Exists in the First Place

A fake wine cellar doesn’t collapse when you put bottle number 501 inside it. It just quietly starts stacking bottles on top of each other and hopes you don’t notice.

That’s exactly how counterfeit USB drives behave.

They lie about capacity.

A drive claims 128 GB. Physically, it might only have 16 GB of real NAND flash. The controller reports the larger number to the operating system, files copy over just fine, and nothing looks wrong — until you pass the real limit.

After that point, new data overwrites old data silently. No warnings. No errors. Just corrupted files later.

H-testing was created to expose that behavior.

What H-Testing Actually Does

An H-test performs a full logical write-and-verify cycle.

First, it writes known data patterns until the drive is completely full — not “mostly full,” but 100% of the reported capacity.

Then it reads all of that data back and checks whether every byte matches what was written.

If something doesn’t match, you’ve learned something important about that drive — and it’s rarely good news.

That’s it. That’s the test.

About the Names (Where Confusion Starts)

The real tool is called H2testw.

The “H” does not represent a hierarchy. The “2” does not represent a level. It is not part of a sequence or scale.

Much later — mostly through marketplace listings, factory QC sheets, and poorly translated documentation — the phrase “H5 test” started appearing.

Here’s the important part:

There is no H5 tool. There is no H1, H3, or H4. There is no progression.

“H5” is informal slang, almost always meaning “we ran an H2-style full-capacity test.”

The Comparison That Actually Matters

“But It Fills the Drive — Isn’t That an Erase?”

Yes, an H-test overwrites the entire logical address space of the USB drive.

No, that does not mean it erases all physical flash memory.

Flash controllers use wear leveling, block remapping, and spare (over-provisioned) areas. Old data can remain in physical NAND blocks that are no longer mapped to any logical address the operating system can see — a behavior explained in more detail in Longevity of USB Flash and Wear Leveling.

From the computer’s point of view, the drive looks clean. From a forensic or compliance point of view, that guarantee does not exist.

This is also why integrity testing and media health checks (like identifying unreadable or failing blocks) are different problems entirely, as covered in How to Check for Bad Sectors on a USB Flash Drive.

The Wine-Glass Takeaway

I finish the explanation, and the CEO nods. He doesn’t need to understand wear-leveling algorithms or NAND remapping tables.

So I give him the version that sticks:

“H-testing is like filling every shelf in the cellar and checking every bottle is still the one you put there. It proves the cellar is real. It doesn’t make the building fireproof.”

That’s the part most people miss.

Final Truth, Minus the Wine

H-testing (H2testw) verifies honesty and reliability — not security. There is no H-scale. There are no levels. And if someone says “H5,” they almost always mean “we ran H2.”

How this article was created: This article was written with AI-assisted research and structuring, then reviewed, edited, and technically validated by a GetUSB.info Editor. Any images used in future updates will be illustrative and not intended as forensic or diagnostic evidence.