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.
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.