Keyboard Tester

What is a keyboard tester?

A keyboard tester is a simple diagnostic tool that shows you, in real time, exactly which keys your keyboard is sending to the computer. You press a key, and the matching key on an on-screen layout lights up. Once you release it, that key stays marked as tested, so you can methodically work across the whole board and see at a glance which keys you have not yet checked.

It sounds basic, but it answers a question that is otherwise surprisingly hard to verify: is this key actually broken, or is it something else? When a letter stops appearing in your documents, the cause could be a dead switch, a stuck key, dirt under the cap, a flaky cable, a remap in software, or even ghosting when you press several keys together. A tester isolates the hardware so you can see the raw signal before you blame anything else.

This tool also shows the three values the browser reports for each press:

• key — the character or name the key produces, such as a, Enter or ArrowLeft. This respects your layout and modifiers, so Shift + 1 reports !.
• code — the physical position on the keyboard, such as KeyA, Digit1 or ShiftLeft. This stays the same regardless of language layout, which is why the on-screen keyboard matches on it.
• keyCode — the older numeric code. It is deprecated in modern web standards but still useful when you are debugging legacy software or comparing notes with older references.

How to use it

1. Click anywhere on the page so the browser is focused, then start pressing keys.
2. Each key you press lights up in the accent colour while it is held down.
3. When you let go, the key stays subtly marked as tested, so you can track your progress across the board.
4. Watch the Last key panel to read the live key, code and keyCode values.
5. Glance at Recently pressed to see a short history of your last presses — handy when a key fires twice or registers the wrong character.
6. Hit Reset to clear all tested marks and start a fresh pass.

To check a keyboard thoroughly, go row by row: function row, number row, the three letter rows, the modifiers, the spacebar, and the arrow keys. If every key lights up and shows a sensible code, the hardware is doing its job.

A few keys are intentionally caught by the tool — Tab, Space, Backspace, Enter and the arrow keys — so the page does not scroll, tab away or navigate back while you test. Function keys (F1–F12) and browser shortcuts are left alone, so you can still open your developer tools or refresh if you need to.

Understanding ghosting and NKRO

If you press several keys at once and some of them refuse to light up, you have probably hit ghosting or a rollover limit — and on most keyboards that is normal, not a defect.

• Ghosting is when a keyboard reports a key you did not press, because of how the key matrix is wired. Good keyboards prevent this with diodes, so instead of a phantom key you simply get a dropped key.
• Key rollover describes how many keys can be registered at the same time. 2KRO or 6KRO means two or six simultaneous keys are guaranteed; cheaper boards may manage only a handful in certain combinations.
• NKRO (N-key rollover) means every key is independent — you can press all of them at once and each one still registers. Gaming and mechanical keyboards often advertise NKRO for exactly this reason.

To tell ghosting apart from a genuine fault, test the suspect keys individually. If each works alone but they drop out in combination, that is a rollover limitation of the keyboard, not a broken switch. If a key never registers even on its own, that points to a real hardware problem.

Debugging stuck and dead keys

When a key misbehaves, this tester helps you narrow down the cause quickly:

• Dead key (nothing happens). No highlight, no change in the last-key readout. Try the same physical key after a restart and in another application. If it is dead everywhere, the switch, solder joint or cable is the likely culprit. On a laptop it may be debris under the key — a careful clean sometimes revives it.
• Stuck key (fires repeatedly or stays down). If a key keeps the highlight on after you release it, or the recent log fills with repeats, it may be physically stuck. Pop the keycap if you can and clear out dust or crumbs. A sticky switch often frees up after cleaning.
• Wrong character. If KeyA reports a different key value, you are almost certainly looking at a software remap or the wrong keyboard layout, not a hardware fault. Check your operating system's keyboard language settings.
• Double presses (chatter). If one tap produces two entries in the recent log, the switch may be "chattering" — a worn contact bouncing. This is common on ageing mechanical switches and usually means the switch needs replacing.

Common mistakes when testing a keyboard

• Forgetting to focus the page. If you clicked into another window, key presses go elsewhere. Click on the page first.
• Blaming the hardware too early. A surprising number of "broken key" reports are actually a remapped key, a stuck modifier, or the wrong layout. The key versus code readout helps you spot this.
• Testing combinations instead of single keys. Ghosting can make a healthy keyboard look faulty. Always confirm a suspect key on its own.
• Ignoring the connection. A loose or damaged cable, a failing USB port, or a low wireless battery can mimic dead keys. Try a different port or a fresh battery before condemning the keyboard.

Used carefully, a keyboard tester turns a vague "some keys don't work" into a precise diagnosis. It runs entirely in your browser, marks your progress as you go, and gives you the exact key, code and keyCode for every press — everything you need to decide whether a clean, a remap or a repair is in order. Once you've confirmed every key fires, gamers often pair this with a CPS test or an APM test to benchmark how fast they can actually drive that input.