Keyboard Tester
Press any key to check it works — with rollover, stuck-key and chatter detection built in.
Last key
- event.key
- —
- event.code
- —
- keyCode
- —
Rollover (NKRO)
Held now: 0 · Max at once: 0
Press as many keys as you can simultaneously to measure rollover.
Health
No chatter or stuck keys detected.
Event log
- Press any key to begin…
How it works
The keyboard tester listens to raw keydown and keyup events straight from your
browser. When you press a key, the matching key on the on-screen keyboard lights up in cyan; when you
release it, it stays dimmed so you can track which keys you have already verified. The live panel shows
the exact event.key, event.code and legacy keycode your keyboard sent —
useful for remapping software and debugging layout issues.
Three health checks run continuously. The rollover counter tracks how many keys are held at once and remembers the maximum — that's your keyboard's real NKRO limit through this browser and connection. The stuck-key detector warns when a key reports held for more than five seconds, which usually means a physically jammed switch or a driver fault. The chatter detector flags any key that registers twice within 30 milliseconds — far faster than any human double-tap and the signature of a worn or dirty switch. Everything runs locally; your keystrokes never leave this page.
A full online key test routine (60 seconds)
To certify a keyboard — before buying second-hand, after a spill, or when a game "randomly" misfires — run this order: type a full sentence and watch for doubled letters (chatter); press every key once, row by row, including F-keys, arrows and the numpad, until the whole on-screen board has lit; hold your main gaming cluster together (W+A+S+D+Space+Shift) and check the rollover counter reaches 6+; then hold each modifier (Shift, Ctrl, Alt, Win) with a letter to confirm combos register. A key that lights on-screen but doesn't type in other apps points to software remapping, not hardware — check language settings and remappers before blaming the board. Keys fine but typing feels slow? That's a different fault: measure it with the keyboard delay test.
Reading your keyboard test results
Every key you press lights up and is logged with three identifiers — event.key (the character produced), event.code (the physical position, independent of layout) and the legacy keyCode. If a key lights up on screen, the switch and the keyboard's controller are physically fine, even when nothing types in other apps. That single fact rules out hardware for most "my key stopped working" cases and points you at software: a stuck modifier, a remap, or a per-app shortcut swallowing the key.
What each health check is telling you
| Signal | What it means | What to do |
|---|---|---|
| Key never lights up | No event reaches the browser — dead switch, broken trace, or an OS-level key (Fn, sometimes PrintScreen) | Test the same key in a text editor; if it fails everywhere, it is hardware |
| Chatter warning | One press registered twice within 30 ms — worn or dirty switch bounce | Blow out debris or apply contact cleaner; if it persists, replace the switch |
| Stuck-key warning | A key reports held for over five seconds without release | Physically free the keycap; check for spilled residue under the switch |
| Keys drop when many are held | Rollover limit reached (ghosting) — normal on membrane boards | Nothing to fix; see the rollover section below |
Rollover (NKRO) explained
Rollover is how many keys your keyboard can report at exactly the same time. Budget membrane keyboards commonly cap at 6-key rollover (6KRO) over USB, plus modifiers — fine for typing, limiting for games that need many simultaneous inputs. NKRO (n-key rollover) means every key registers no matter how many you hold. Hold a fistful of keys and watch the "Max at once" counter to find your real ceiling. If it stalls at 6, that is your keyboard's matrix, not a fault.
Common questions this test settles
- Is my key physically broken or is it software? If it lights up here, it is software.
- Why won't W+A+Space work together in my game? Rollover ghosting — check your max simultaneous count.
- Is my new keyboard double-typing? The chatter detector confirms switch bounce objectively.
Troubleshooting
› A key lights up but nothing types — is it broken?
No. The tester listens to raw key events, so a key can register here even if a remap or software blocks its normal output. If it lights up, the switch and controller are working.
› PrintScreen, Fn or the Windows key don’t register
Some keys are intercepted by the operating system before they reach the browser. Fn is handled inside the keyboard itself and never sends an event. This is a platform limitation, not a fault.
› Several keys stop registering when I hold many at once
That is rollover blocking (ghosting). Many office keyboards register only 6 keys at once over USB. Use the rollover counter to see your keyboard’s real simultaneous-key limit.
Frequently asked questions
› Is this keyboard tester free?
Yes — completely free, no download, no sign-up. It runs entirely in your browser.
› Do my keystrokes get uploaded anywhere?
No. Every key event is processed locally in your browser and never leaves your device.
› What is key rollover (NKRO)?
Rollover is how many keys your keyboard can register at the same time. NKRO means every key registers no matter how many are held. Hold multiple keys in the tester to measure yours.
› What is key chatter?
Chatter is when one physical press registers twice due to a worn switch. The tester flags any key that double-registers within 30ms.
› Does it work with wireless keyboards?
Yes — Bluetooth and 2.4GHz wireless keyboards send identical key events to the browser, so everything works the same.