How to test a keyboard

Testing a keyboard does not require special software when you just need to know whether every key reaches the browser. A keyboard test page listens for keydown and keyup events and displays the physical code, the produced key, and the modifier state.

Run the three-pass test

1. Press every key once, top row to bottom row. Watch the on-screen keycap light up and confirm the event.code matches the position you pressed.
2. Hold each key for about two seconds. A healthy key produces one repeat stream after the OS repeat delay; a switch that jitters may fire repeats immediately or release by itself.
3. Press each modifier with a letter, such as Shift + A or Ctrl + C. If the browser opens a menu or performs a shortcut instead, that is a browser limitation, not a keyboard result.

An original example: type the quick brown fox while watching the event sheet. Every letter should map to a KeyX style code, and the history should show no phantom keyup between keystrokes.

What a passing test looks like

A key that passes lights up on keydown, releases on keyup, and does not appear in the repeat or stuck list while idle. If a key never lights up, test it in a text editor and on a second keyboard before assuming the switch is faulty.