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Key Rollover Test

Find out how many keys your board reports at once.

100% LocalFree

Hold several keys down together and watch the counter. Add one more each time until a key stops appearing: that is where your keyboard gives up.

Held now
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Most at once
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  • No keys held.

How to test key rollover

  1. 1 Hold one key, then add a second, a third and so on without letting go. The counter shows how many the browser can see at the same time.
  2. 2 Try the combinations you actually use. On a keyboard shared with games, hold shift, W and space together and see whether all three register.
  3. 3 Watch for a key that never appears. That is ghosting: the keyboard's wiring cannot tell the combination apart, so it drops one rather than guess.
  4. 4 Modifier keys are cheap. Ctrl, Shift and Alt sit on their own lines in most keyboards, so they rarely count against the limit.

Frequently asked questions

What is key rollover?
It is how many keys a keyboard can report at the same time. Cheap boards share wiring between keys and can only resolve a few simultaneous presses; better boards give every key its own path, which is called n-key rollover.
What is ghosting?
When a keyboard cannot tell two combinations apart, it either drops a key or reports one you never pressed. The dropped variant is far more common today and is what you will see here as a key that refuses to appear.
Why does my keyboard stop at six?
The standard USB keyboard protocol carries six keys plus modifiers, which is a deliberate limit rather than a fault. Keyboards with full rollover use a different reporting mode to get past it.
Does the browser limit what I can test?
Slightly. A few combinations are reserved by the operating system and never reach the page, and the Fn key is usually handled inside the keyboard itself. For everything else, what you see here is what a game would see.

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