Test keyboard rollover online and see how many keys your keyboard can detect at once. Check multi-key input, gaming combinations and possible ghosting directly in your browser.
Click here & press multiple physical keys simultaneously.
Physical keystrokes received live via KeyboardEvent.code.
Press Esc
anytime to release focus.
Test specific gaming clusters to identify missing keys, blocking, or phantom events.
These results show what your keyboard and browser reported during this session. They do not certify the keyboard's hardware rollover specification. Matrix throughput, operating-system hotkeys, and USB controller descriptors may produce different behavior on different ports or systems.
When you press physical keys on a keyboard, input data travels through a multi-stage hardware and software pipeline:
What this test observes: This web instrument tracks physical keystroke concurrency using standard W3C KeyboardEvent.code identifiers, filtering out synthetic auto-repeats (event.repeat === true) to measure exact simultaneous keydown/keyup state.
Browser limitations & OS-reserved hotkeys: Certain system shortcuts (such as Ctrl+W, Ctrl+T, Alt+Tab, F11, or hardware Fn layer keys) are intercepted by the operating system or browser shell before JavaScript receives them. A missing event for a reserved system shortcut does not indicate a defective keyboard switch.
2KRO allows only two simultaneous keys (common in basic office keyboards). 6KRO handles six alphanumeric keys plus modifiers via standard USB HID protocol. NKRO handles unlimited simultaneous keypresses via discrete diodes on every switch.
Standard USB HID reports pass an 8-byte payload (1 modifier byte, 1 reserved byte, 6 keycode bytes). NKRO gaming keyboards emulate multiple virtual HID endpoints or use bitmap report descriptors to send all key states in real time.
Games like OSU!, StepMania, and competitive fighting games demand zero key blocking during rapid multi-finger inputs. NKRO prevents missed chords during high APM (actions per minute) gameplay.
Web browsers process physical keyboard inputs asynchronously. Calculating exact peak simultaneous keys over time provides a reliable observational benchmark for real-world web gaming performance.
Quick answers about how this tool works.
Plain-language explainers that sit next to this tool.
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