How to test a keyboard (ghosting, dead keys and key rollover)
Whether you're buying a used keyboard, troubleshooting a sticky key, or checking a new mechanical board, a quick key test tells you everything. Here's what to look for — including two things gamers obsess over.
The basic test: does every key register?
The simplest check is to press every key and confirm each one registers exactly once. A key tester lights up each key as you press it, so you can immediately see:
- Dead keys — press it, nothing happens. Could be debris, a failed switch, or a controller fault.
- Chattering keys — one press registers as two or more. Common on worn mechanical switches.
- Sticky keys — the key stays "down" after you release it.
Work across the whole board, including modifiers (Shift, Ctrl, Alt), function keys, and the numpad, which are easy to forget.
Ghosting — when presses go missing
Ghosting is when pressing several keys at once causes some presses to be lost or phantom keys to appear. It comes from how the keyboard's internal grid is wired: certain key combinations can't all be read simultaneously on cheaper boards. You'll notice it in games ("I pressed forward + left + jump but didn't jump") or fast typing.
N-key rollover — the fix
Key rollover is how many simultaneous keys a board can register reliably. "6-key rollover" handles six at once; N-key rollover (NKRO) means every key is independent — press as many as you want, all register. Gamers and fast typists want NKRO so no input is ever dropped. You can test it by holding down several keys at once and watching whether they all light up.
When to test
- Buying a used or refurbished keyboard — verify before you pay.
- Diagnosing a specific key that seems flaky.
- Checking a new mechanical board's rollover and switches.
Pair this with a quick screen check when inspecting a used laptop — the two together cover the most common hidden faults.