Instrument 01 · keyboard
Keyboard tester
Press keys and watch the board answer. Keys you have verified stay marked; a key that never lights while pressed is your fault, found.
Test the rest of your setup
How to read your results
Every key you press lights on the board and stays marked. Work across the keyboard row by row; any key that never lights while physically pressed has a fault between the switch and the USB report, and you have just confirmed it in the cleanest environment your computer offers. The rollover counter shows how many keys your keyboard reports simultaneously: 6 is standard for office boards, while gaming keyboards commonly report full N-key rollover.
Common fixes for a dead key
- Debris under the cap: the cause in most cases. Pull the keycap and clear the switch with air; a single crumb can block actuation.
- Mechanical boards: reseat or hot-swap the switch if your board allows it; a failed switch is a two-minute part swap, not a new keyboard.
- Whole row or column dead: that is a matrix trace or controller fault, not dirt. Warranty it or retire it.
- Key works here but not in a game: the hardware is fine; look at key bindings and background software capturing the key.
- Laptop keys: a spilled-on membrane rarely recovers. Confirm with this test, then price the top-case replacement against an external board.
Ghosting, explained in one paragraph
Hold two keys and press a third. On cheap matrices some three-key combinations either drop a key (ghost) or invent one (phantom). If you game with WASD plus modifiers, test exactly those clusters here; the held counter tells you the moment a press stops registering.