How to test your keyboard
Press every key once. Each key you press turns pink and stays lit, so any key that stays grey after you have pressed it is either dead or not reporting correctly. The panel shows the key value (the character produced), the code (the physical key position), the legacy keyCode and the location (left, right or numpad).
Ghosting and N-key rollover
Ghosting happens when a keyboard cannot register several keys pressed together. Hold down keys one by one, for example A, S, D, F, then J, K, L, and watch the “Held now” counter. Cheap keyboards often stop at 2 or 3 keys in some combinations; gaming keyboards with 6KRO or NKRO handle 6 or more. Note that a USB keyboard can still be limited by the OS or a hub.
Stuck or chattering keys
If a key stays lit in “Held now” after you release it, or appears twice for one press, the switch may be dirty or worn. Try cleaning under the keycap with compressed air, then test again.