Key rollover and ghosting test
Some combinations never reach the browser because your operating system takes them first - Alt+Tab, the Windows or Command key, and the media keys. Those not appearing here is not a fault with your keyboard.
Rollover, ghosting and blocking
This finds a different fault from a dead key. A keyboard wires its keys into a grid and shares connections between them, so some combinations are electrically indistinguishable from others. Press the wrong three together and one of two things happens:
- Blocking - a key you pressed is not reported. The common one, and what stops you moving diagonally while doing anything else.
- Ghosting - a key you did not press is reported. Rarer on modern keyboards, which mostly prevent it by blocking instead.
Rollover is how many keys can be reported simultaneously. "6KRO" means six; "NKRO" means no fixed limit.
How to test
- Hold as many keys as you can at once and watch the "most at once" figure.
- Try the combinations that matter to you. For games that is usually W, A, S, D plus space, shift and a number.
- Try three letters physically close together - neighbouring keys often share grid connections, so those fail first.
- Press Reset and repeat with a different group.
What the numbers mean
| Most at once | What you have |
|---|---|
| 2 | A basic membrane keyboard. Fine for typing, limiting in games. |
| 3 to 5 | Typical of an inexpensive keyboard or a laptop. |
| 6 | 6-key rollover, the classic USB limit. Ample for nearly everything. |
| 7 or more | Full N-key rollover. Nothing you do will exceed it. |
Modifier keys - shift, control, alt - are usually handled separately from the grid and do not count against the limit, which is why six letters plus shift often works when seven letters does not.
What this test cannot see
Some combinations never reach the browser at all, because the operating system takes them first. Alt+Tab, the Windows or Command key, Cmd+Q and the media keys are intercepted above the browser. Their absence here is not a fault with your keyboard, and no browser-based test can measure them.
Keys are identified by physical position rather than by the character they produce, so the result does not change with your keyboard layout or with shift held down.
Is low rollover worth replacing a keyboard over?
For typing, no - nobody types fast enough to hit the limit. For gaming it is a real constraint: two-key rollover means you cannot walk diagonally and jump at the same time. If that is your situation, look for a keyboard stating 6KRO or NKRO. Mechanical keyboards usually have it, though note that some deliver full NKRO only over the older PS/2 connection rather than USB.
Related checks
Our keyboard tester finds keys that do not register at all, which is the other common keyboard fault.
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