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Keyboard ghosting and rollover test

Hold several keys at once — the way you do in games — and see how many reach the computer together. Guided combinations show exactly which keys go missing.

Press Start full capture, then hold the keys of a combination at the same time. Esc twice or Stop to exit.

Keys held now
0
Most keys at once
0

Held now: —

Largest combination seen: —

Combinations to try

Hold all keys of a row at the same time. Keys light up as the browser receives them; a row turns green when every key in it arrived together.

    How to run the test

    1. Press Start full capture so Space, Tab and other keys are not used by the browser.
    2. Pick a combination from the list and hold all its keys at the same time.
    3. Each key lights up while the browser receives it. If one stays dark while you hold it, the keyboard did not report it.
    4. Try the combinations you actually use in games, and watch Most keys at once.

    Ghosting, blocking and rollover

    • Key rollover is how many keys a keyboard can report at the same time. Many office keyboards handle 2–6 keys in some combinations; gaming keyboards often advertise 6-key or N-key rollover.
    • Blocking (jamming): a key you press is not reported because of the keys already held. This is what the test catches.
    • Ghosting, in the strict sense, is an extra key reported that you did not press. Modern keyboards usually block instead of ghosting; if a key appears that you are not touching, note the combination.
    • Limits depend on which keys are combined, not just how many, because keys share circuits in the keyboard matrix. That is why several different combinations are listed.

    What the result does not prove

    The test shows the keys this browser received. It cannot certify NKRO: some keyboards switch to 6-key mode over USB for compatibility, some systems or browsers limit simultaneous keys, and the number of fingers you have is a limit too. A combination that fails here but matters to you is worth retesting on another USB port and in the keyboard's software (look for a 6KRO/NKRO setting).

    Questions

    What does N-key rollover mean?

    That every key can be reported at the same time, whatever else is held. In practice you need far fewer: most games use up to five or six keys together.

    Is my keyboard faulty if a combination fails?

    Not necessarily. Most keyboards have combination limits by design. A fault is more likely if the same key fails on its own or in every combination — check it with the keyboard test.

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