Keyboard Rollover Test

How to use

1. Use Free mode to explore how many simultaneous key events reach the browser, or Guided combination mode when you want to test a known combination.
2. In Guided mode, choose a preset or record a custom combination, then press Start guided round.
3. Press and hold all expected keys at the same time. Keep them held together briefly, then release all keys to complete the round.
4. Review Best simultaneous match, Registered together, Possible missing together, and any Unexpected codes observed.
5. Repeat several combinations that matter to your actual use. Reset clears the current session's free peak, guided rounds, and custom combination.

What the result means

• Currently pressed shows the codes the browser presently considers held. Max held together observed is the largest simultaneous browser-reported set seen in this session.
• The maximum simultaneous keys value is a browser-observed count, not a hardware rating.
• Guided best match is the largest number of expected codes that were present together at one instant. Registered together lists the expected codes in that actual state.
• Possible missing together lists expected codes not present in the best simultaneous state. Unexpected codes are browser codes outside the expected set that appeared during the controlled round.
• A successful round validates only that tested combination at the browser level. One successful six-key combination does not certify universal 6KRO or NKRO.
• A missing code alone cannot prove whether the cause is the keyboard matrix, firmware, connection/reporting protocol, OS shortcut, browser/software handling, focus, or interruption.
• The guided analysis listens to browser keydown/keyup events, uses KeyboardEvent.code, ignores repeat keydowns for concurrency, replays the round chronologically, and reconstructs which codes were down together; it does not union every code seen during the round.
• Rollover describes simultaneous key-reporting behavior. NKRO is a broad capability claim, not a score this page can certify; ghosting or blocking language describes observed combination behavior, not a proven matrix fault.
• This is browser-observed rollover evidence, not electrical NKRO certification; this browser result is not NKRO certification, and a possible missing browser event is not automatically a hardware fault.

Limitations

• Browser results show only key events delivered to this page. A successful combination does not certify all combinations or full NKRO, and a missing event does not by itself prove a hardware fault.
• The operating system or browser may intercept shortcuts before their key events reach the page.
• The page cannot independently verify which physical keys your fingers touched, so an unexpected browser code may be accidental, remapped, software-generated, or phantom-like without proving hardware ghosting.
• Different combinations can behave differently. Browser-observed evidence is not a full hardware matrix, firmware, report-protocol, or electrical certification.

Troubleshooting

A shortcut combination is incomplete

Try a combination that is not reserved by the operating system or browser, keep this tab focused, press all expected keys together, release all keys, and repeat the same guided round.

The result says Possible missing even though every key worked individually

Individual registration and simultaneous rollover are different tasks. Repeat the exact combination; a keyboard can report each key alone yet fail a particular multi-key combination.

Guided results change between runs

Press all expected keys together rather than sequentially, hold them briefly, then release all. Compare repeated identical combinations under the same focus and browser conditions.

A round was interrupted

Focus loss or page hiding invalidates the guided round. Return to the page and start a fresh round; interrupted rounds are not classified.

Related tools

• Keyboard Tester

  Test keyboard keys online with Windows full-size, TKL, MacBook/Apple, and 60% layouts. See pressed/tested keys, event.key/event.code, repeat status, and untested keys.

• Keyboard Polling Rate Test

  Check browser-observed keyboard event timing in single-key, alternating-key, and auto-repeat modes. See event Hz, intervals, consistency, and local history—not raw USB polling.

• Keyboard Chatter Test

  Check possible keyboard chatter and double presses with controlled keydown/keyup timing. Test one key or scan multiple keys, review per-key flags and local history; auto-repeat is excluded.

FAQ