Keyboard ghosting test (NKRO test)
This keyboard ghosting test shows every key your board actually reports while you hold combinations down. Stack up keys, watch the live count, and find out if you have n-key rollover, a 6-key cap, or combos that silently drop. Your best result is saved between visits.
Held right now
0
Max at once (record)
0
0 without modifiers
Max letters at once
0
Keys the browser sees held down
Press and hold keys on your physical keyboard. Every registered key appears here instantly.
Rollover verdict: Not tested yet
Record: 0 keys at once, 0 of them non-modifier keys, 0 of them letters.
Click the test area (or just start pressing) and hold down as many letter keys as your fingers allow.
Blocking check: a key you are physically holding that never shows a chip above was dropped by the keyboard on that combination, either a rollover limit or matrix blocking. No software can fix it.
Ghosting check: a chip that appears for a key you are not touching is a phantom press, the classic non-diode matrix fault. Watch the list closely while you hold the Center block combo below.
Combos worth trying
- Column stack: Q + A + Z, then add W + S + X, then E + D + C Same-column keys share matrix lines; cheap boards ghost here first.
- Shift cluster: Left Shift + Right Shift + A + S + D + F Modifier plus alpha combos expose blocking on budget boards.
- Gaming cluster: W + A + S + D + Space + Left Shift + Left Ctrl The exact combo that fails mid-game if your board blocks.
- Home row sweep: A + S + D + F + J + K + L + ; Eight spread-out alphas: passes on 6KRO boards will cap at 6.
- Center block: T + Y + G + H + B + N A tight physical square, the classic ghosting trap on non-diode matrices.
Tip: your OS may swallow certain combos (three or more with Ctrl or Alt can trigger shortcuts). Stick to letters, Shift and Space for a clean rollover read.
Space, Backspace, slash and apostrophe are captured on this page, so holding them cannot scroll the tool away, navigate back or open quick find. Arrow and Page keys still scroll.
How the ghosting and rollover test works
Every key your keyboard successfully reports fires a raw keydown event with a physical
event.code, and this page turns each one into a live chip the instant the browser sees it. That
exposes both faults at once: if your finger is on a key but no chip appears, the keyboard never sent it, and if
a chip appears for a key you are not touching, the matrix invented it. The counter tracks how many keys are held
simultaneously, and your record is stored locally so you can retest after firmware changes or a mode switch. A
restored record is labeled as coming from a previous session, so it is never mistaken for a live pass on a
keyboard you just plugged in.
The verdict logic is deliberately conservative, and it counts the way the USB spec does. The 6-key boot-protocol cap is 6 simultaneous keys plus modifiers, so Shift, Ctrl, Alt and the Windows or Command key are excluded from the threshold; a board that reports 6 letters plus two modifiers has not beaten 6KRO, it has exactly hit it. Holding 10 or more letter keys at once with all of them registering is treated as strong evidence of NKRO. Passing 6 non-modifier keys rules out the boot-protocol cap. Non-modifier keys pinned at exactly 6 while you are clearly holding more suggests 6KRO, which many boards use by default for BIOS compatibility and some can disable. The record tile still shows the raw total including modifiers, because that is what the browser genuinely received.
Reading your result honestly
A browser can only see what the operating system passes through, so a handful of missing combos does not always mean bad hardware: the OS eats shortcuts involving Ctrl, Alt and the Windows or Command key, and macOS suppresses some events entirely. That is why the suggested combos in the tool lean on letters, Shift and Space, which reach the page cleanly on every platform. Test the clusters you actually use, especially the gaming cluster around W, A, S and D, because that is where blocking hurts in practice.
Rollover is only one health check. To verify every individual key works, run the full keyboard tester. If a key registers twice per press, that is a different fault: measure it with the key chatter test. Curious how fast your browser pipeline responds to a press? The latency test measures exactly that, with honest caveats. And if this test exposed a board that blocks your gaming combos, our best switches for gaming guide covers what to look for in a replacement.
Frequently asked questions
What is keyboard ghosting?
Ghosting happens when you hold several keys and the keyboard either drops one of them or invents a phantom press it cannot tell apart from a real one. It is caused by the switch matrix: without a diode per key, certain three-key combinations create an electrical path that looks like a fourth key, so the controller blocks or misreads the combo. This test shows both halves. A key you are physically holding that never appears in the held-keys list has been blocked or has hit the rollover limit; a key that appears in the list while your finger is nowhere near it is a true phantom (ghost) press.
What is n-key rollover (NKRO)?
N-key rollover means every key you press registers correctly no matter how many others are already held. Boards with per-key diodes and NKRO firmware can report the entire keyboard at once. If you can hold 10 or more letter keys in this test and all of them show up, your keyboard almost certainly has NKRO.
Why does my count stop at exactly 6 keys?
That is 6-key rollover (6KRO), the limit of the classic USB boot-keyboard protocol: 6 simultaneous keys plus modifiers. Many keyboards default to this mode for BIOS compatibility. Some boards can switch to full NKRO with a key combo, a switch on the case, or by using their software, so check your manual before assuming the hardware is limited.
Is 6KRO bad for gaming?
Usually not. Very few games need more than 6 simultaneous keys plus modifiers. The real problem is ghosting and blocking on cheap membrane boards, where common gaming clusters like W+A+Space+Shift can fail with only 3 or 4 keys held. Test the exact combos you use in-game; the suggested combos in the tool cover the usual trouble spots.
Why do some key combos not register even on a good keyboard?
Your operating system and browser grab some combinations before a web page sees them: Ctrl and Alt shortcuts, Windows-key combos, and media keys are common examples. Certain laptop keyboards also share matrix lines aggressively to save space. For a clean rollover reading, test with letter keys, Shift and Space rather than modifier-heavy combos.