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N-Key Rollover Test — Check 2KRO, 6KRO and NKRO

Hold letters and numbers together to count simultaneous non-modifier key events. The highest observed combination is a lower bound, not proof of full NKRO.

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Free to use · Browser based · How we test

Press a physical key to start — no click needed. Tab moves between controls, and browser shortcuts remain available.

Observed Rollover Result
—

No combination observed

Hold letters or numbers together. Modifiers are counted separately.

Max simultaneous keys0
x
02 keys6 keys10 observed

Currently held, including modifiers: 0 key(s)

What your rollover result actually proves

Key rollover describes how many simultaneous keys a keyboard can report correctly. A 2KRO specification promises combinations of two keys; 6KRO promises combinations of six. Full NKRO means all supported keys can register together. One successful combination does not establish a guarantee for every other combination.

This test records the largest non-modifier combination delivered to this browser. If seven letters register together, that combination exceeded six keys. If only six register, possible causes include the keyboard report format, firmware mode, matrix blocking, a KVM, or software interception. The page cannot identify which layer imposed the limit.

Shift, Control, Alt and Windows or Command use separate modifier bits in the standard USB boot-keyboard report. They are excluded from the peak used here. The live held list still shows them so you can check combinations involving modifiers.

The standard USB boot-keyboard report has slots for six ordinary key codes plus modifiers. Other report formats can support more. USB alone does not tell you a keyboard's rollover capability, and PS/2 alone does not remove a keyboard matrix limitation.

Repeat the combinations used in your games or application. A board might accept ten home-row keys yet block one particular movement combination. Use the ghosting test to compare the keys you physically hold with the events actually received.

Read how our browser tests work for event handling, measurement limits, and privacy details.

Key Capabilities & Features

2 keys observed

This pair worked. It does not establish a two-key maximum or certify every possible pair.

6 keys observed

Six keys reached the page together. A plateau at six can have several causes; check the device mode.

7 or more observed

The tested combination exceeds six ordinary keys. This still does not certify full NKRO.

Modifiers tracked separately

Shift, Ctrl, Alt and Meta remain visible but do not inflate the non-modifier peak.

How to Perform This Test

  1. Baseline: press A and S together.
  2. Six-key check: hold Q, W, E, A, S and D, then add R. Check which codes appear.
  3. Vary the combination: try different rows and the number keys. Release everything between attempts.
  4. Compare modes: repeat through the same USB connection, then wireless if supported. Consult the keyboard manual for its rollover setting.
  5. Record the result: describe it as “at least X non-modifier keys observed” and list the combinations tested.

Troubleshooting Common Hardware Issues

  • A key works alone but vanishes in a chord: repeat that exact chord and compare with a different browser or direct USB connection.
  • The result changes through a KVM or wireless connection: test each input path separately and consult the device specifications.
  • A shortcut opens an OS panel or switches tabs: it may never reach the page. Browser and OS reserved shortcuts are outside this test.
  • The count remains high after switching away: held state clears when focus is lost; release all keys and begin a new combination.

Frequently Asked Questions

Does ten keys mean full NKRO?
No. It establishes that one ten-key combination was observed. Full NKRO is a broader capability that cannot be certified from a small set of browser trials.
Why are modifiers excluded from the main count?
The standard USB boot-keyboard report represents modifiers separately from its six ordinary key slots. Counting them together can make a six-key report appear to support more ordinary keys.
Can software upgrade a 6KRO keyboard to NKRO?
Only if the keyboard already supports a different report mode or firmware capability. A browser cannot change its switch matrix or firmware.

Further Reading

Start again with the full keyboard test, compare the keyboard event reference, or choose the next test in the diagnostic tools hub.

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