N-Key Rollover (NKRO) Tester

N-key rollover means a keyboard can register every key in the relevant set simultaneously. This page shows the key events your browser receives for the combinations you try. A high count alone does not certify the keyboard’s NKRO specification.

6KRO commonly describes support for six ordinary keys at once, with modifier keys often handled separately. This tester counts every distinct recognized code it receives, including modifiers. Its total is not a direct hardware 6KRO rating.

Ghosting is an unintended phantom key appearing when you did not press it. Compare the highlighted keys with your physical actions. The page cannot know which keys you intended to press, so it does not automatically detect or rule out ghosting.

Blocking is an intended key not registering during a combination. If a key does not appear, try it alone and in different combinations. Keyboard circuitry, connection mode, operating-system shortcuts, browser focus, and input settings can all affect what reaches the page.

No. Anti-ghosting generally describes measures to prevent phantom input, sometimes for selected combinations. It does not by itself promise that every combination of keys will register. Check the manufacturer’s stated scope and test the combinations you use.

Select the test area, hold several keys together, and compare your intended combination with the highlighted keys and current count. Release them, repeat with other combinations, and review the maximum. Use Reset tested keys or Reset maximum count when you want a fresh comparison.

The browser only sees events delivered to this page. Click the test area again, leave IME composition, and try a key alone. Print Screen, volume keys, system keys, and reserved shortcuts may not be delivered. A missing event alone does not prove a faulty keyboard.

Yes, with a physical keyboard and a supported browser. Choose a Windows or Mac display with Japanese or US labels. The display does not detect your keyboard or change the operating-system input layout. Reserved keys differ by platform. Without an explicit layout choice, the English page starts with Windows US. A manually selected layout is kept when changing languages.

Yes. Firmware, connection mode, input reports, the operating system, and browser behavior can affect delivered events. Compare connections using the same combinations and settings. This tool does not inspect USB descriptors or Bluetooth reports directly.

No. The maximum records the largest number of distinct recognized codes held together in the combinations you tried. It includes modifiers and does not prove that every other combination works or that ghosting is absent.

No. Held keys are counted once, and repeated keydown events do not increase the simultaneous count. Use the separate Keyboard Chatter & Double-Typing Test for repeated inputs, intervals, hold tests, and reports.

Diagnostic input is processed on this page and is not uploaded. Explicit layout preferences are saved locally. Only when you change languages, the maximum, tested key codes, and layout use a one-use session handoff valid for 30 seconds; the receiving page removes it. Held keys are released. No typed-text history is saved.

A physical keyboard is needed for simultaneous-key input; tapping the pictured keys does not simulate a hardware test. The display scrolls on narrow screens. This tester has no report export. Note your observations before closing or reloading the page.