Keyboard Key Not Working: Switch or Computer? How to Tell
If a key does not light up in a browser keyboard test, the keyboard never sent it — that is hardware, and no driver, remap or OS setting will bring it back. If it lights up but nothing appears in your document, the keyboard is fine and the problem is software. That one distinction is what a keyboard test is for, and it takes about a minute.
Why a browser is enough
Search for a keyboard tester and a surprising number of results want you to install an application first. For a check this short that is a strange trade: you are installing software to find out whether hardware works. A browser already receives every key event the keyboard sends, which is enough for the three things people actually want to know.
Check 1 — keys that stopped responding
A dead key usually arrives one of two ways: something was spilled, or one finger landed in the same place for a few years. Walking the whole board and watching which keys register finds it quickly, and it also finds the case people miss — a key that works most of the time and drops one press in ten. That intermittent version is easy to blame on typing speed until you watch it fail on screen.
If a key is genuinely dead, two things are worth trying before replacing the board. Pull the keycap and clean underneath, since debris under a switch is common and costs nothing to rule out. Then plug the keyboard into a different computer. A key that is dead on both machines is the keyboard; a key that works on the second machine is something in the first machine's software.
Check 2 — keys that fire on their own
The opposite fault is a key that repeats, or that sends input you did not type. On screen this looks like the computer misbehaving, which is why it usually gets blamed on the operating system. A browser test shows the key events arriving one by one, so a switch that sends two presses from one push, or that holds itself down, is visible as it happens rather than inferred afterwards.
This matters most with the modifier keys. A Shift or Ctrl key that sticks down changes the behavior of every other key on the board, and the symptom — everything suddenly typing in capitals, or ordinary letters triggering shortcuts — looks nothing like a stuck key until you see it register.
Check 3 — how many keys register at once
The third check is the one almost nobody runs before buying. Keyboards differ in how many simultaneous presses they can report, and cheaper boards stop registering after a small number. Over USB, the standard keyboard report carries six keys plus modifiers, and boards that go beyond that have to do something custom — which is what "N-key rollover" on a spec sheet means.
The number that matters is not the one on the box, though. It is where your board stops on the key combinations you actually use, and the only way to know is to hold several keys down and watch how many arrive. Boards that block early tend to block unevenly, failing on one cluster of keys while handling another fine.
Our keyboard test shows the full layout and lights up each key as its event arrives, so all three checks happen in a single pass — no install, nothing uploaded.
A key that fails on a mechanical board has one more branch worth knowing: on a hot-swap board the switch itself can be replaced without soldering, which turns a dead board into a five-minute repair. We wrote that up separately in what to do when one key on a mechanical keyboard stops working.
Reading the result
A key that never lights up is hardware. A key that lights up but produces nothing in your text editor is software — a remap, a language layout, or an application capturing the key. A key that lights up twice from one press is a failing switch, the same wear pattern that makes mice double-click. Knowing which of the three you have decides whether the fix costs nothing or costs a new keyboard.
Related Desk Armory note
A key that never registers and a key that registers twice need opposite diagnoses. If the browser receives rapid duplicate events from one deliberate tap, use Keyboard Chattering Fix.
How this note was made
Desk Armory built the browser keyboard test to show which physical key codes reach the page. That result separates "no event reached the browser" from "an application ignored the event," but it cannot electrically identify a failed switch, socket, matrix trace, or controller without opening and probing the keyboard.