Keyboard Tester
| Symptom | What this page shows | Likely cause |
|---|---|---|
| a key never lights up | press never registers | dead switch or broken trace |
| chatter suspects > 0 | double presses under 60 ms | worn or dirty switch |
| key stays lit | keydown without keyup | stuck key or OS capture |
| wrong key lights up | code mismatches the legend | remap software is active |
Click the keyboard below, then press every key on your real one - each key lights up the instant it registers. The tester counts every genuine press and runs one diagnostic at the same time: two presses of the same key closer than 60 milliseconds apart are flagged as chatter suspects, the worn-switch signature that turns 'hello' into 'hhello'.
A key that never lights is a dead switch or a broken trace; a key that lights but keeps glowing after you release it is reporting a keydown with no matching keyup - a stuck key or another program swallowing the release. Both take ten seconds to find here instead of ten minutes inside a text editor.
How to use
- Click anywhere on the keyboard card so the page has focus, then press keys on your physical keyboard - each one lights up as it registers.
- Work through every key, especially the ones you type least: F-keys behave like the letter row here, and the numpad lights its own keys.
- Watch the chatter counter while tapping your suspect keys - any count above zero on a key you pressed once means the switch is double-firing.
Frequently asked questions
What is key chatter and why does my keyboard double-type letters?
Mechanical and membrane switches wear with use; a tired switch can close its contact twice inside one press, and the computer faithfully reports two keystrokes. The tell-tale sign is letters that double only sometimes - 'hello' typed slowly is fine, but fast typing produces 'hhello'. This tester flags any two genuine presses under 60 ms apart, far faster than a human re-presses.
A key lights up but no letter appears in my text box - which one is broken?
Neither. This page listens at the keyboard-event level, so it sees keys that your current application ignores or remaps. If the key lights here but does nothing in a text editor, the keyboard hardware is fine and the remapping software or the app's own shortcuts are the place to look.
Can I test a laptop keyboard with this?
Yes - laptop, external, mechanical or membrane all report through the same browser events. Just click the card first so the browser window has focus; unresponsive results almost always mean the click happened in another window.
Does this work on a phone or tablet?
Only partially. Touch screens have no physical key events to catch, so there is nothing to test - open this page on a device with a real keyboard. The on-screen layout itself is a diagram, not a touch keyboard.