Keyboard Ghosting Test & N-Key Rollover (NKRO) Check Online

This keyboard ghosting test shows how many keys your keyboard can register at once and which combinations it silently drops. Hold down any group of keys — W, A, Shift and Space, or a whole handful — and the on-screen layout lights up every key the browser actually receives. A peak counter keeps your highest simultaneous total of ordinary keys — Shift, Ctrl, Alt and Win/Cmd are tallied on their own, because USB sends them in a separate byte — and rates the board as 2-KRO, 6-KRO or full NKRO. Nothing is installed, and no keystroke leaves your browser.

What is keyboard ghosting?

Keyboard ghosting is when a keyboard fails to report a key you are physically holding, because of the combination it is part of. You feel the switch bottom out, but the character never arrives and the game never jumps. The word originally meant the opposite problem — a phantom key appearing on screen that nobody pressed — and both come from the same cause.

Every keyboard is a grid. The controller does not have a wire per key; it has a set of rows and columns, and each switch sits on one crossing. It energises one row at a time and checks which columns respond, hundreds of times a second. Press three keys that share rows and columns — say Q, E and A in the same block — and a fourth crossing completes as well. The controller cannot tell the real press from the phantom one.

Old boards let the phantom through, which is where the name came from. Modern boards do the safer thing: when the pattern is ambiguous they block, dropping one of the keys rather than inventing one. That is why a keyboard ghosting test today usually finds a missing keypress rather than an extra one, and why the result depends on which keys you press, not how many.

What is N-key rollover?

N-key rollover (NKRO) means every key is reported independently, no matter how many others are held down. Manufacturers get there by putting a diode behind every switch, so current can only flow one way through the matrix and a phantom crossing can never complete.

The second half of the problem is the cable. The standard USB HID keyboard report has room for exactly six key codes plus one byte of modifier bits (the two Shifts, Ctrls, Alts and Win/Cmd keys). That is the boot protocol format, kept simple so a BIOS can read it before any driver loads. A keyboard that only ever sends that report is capped at six regular keys no matter how good its matrix is.

USB is not actually the limit. A keyboard can declare a custom HID report, or send several reports in parallel, and pass an unlimited number of keys — this is how NKRO-over-USB boards work, and how QMK and VIA firmware expose an NKRO toggle. PS/2 keyboards avoid the six-slot report entirely, but the matrix still has to support NKRO for that to matter.

2KRO vs 6KRO vs NKRO

Your keyboard ghosting test result falls into one of three tiers:

2KRO — two keys, sometimes three if they sit on different rows. Typical of old membrane office boards and some budget laptops. This is where W + Shift + Space fails.
6KRO — six regular keys plus up to eight modifiers, the USB boot-protocol standard and by far the most common result. Enough for essentially all typing and most gaming.
NKRO — no practical ceiling. Every key is diode-isolated and reported separately. Standard on enthusiast mechanical boards, common on gaming boards, and often switchable so the keyboard still works in BIOS.

Marketing muddies this. "Anti-ghosting" is not a synonym for NKRO: it usually means the maker added diodes to a chosen subset of keys — normally the WASD cluster and modifiers — so the popular gaming combos survive. A board sold as "19-key anti-ghosting" handles 19 specific keys, not any 19 you pick.

How to read your result

Press and hold keys one at a time, adding more without releasing any. The peak counter shows the highest number of ordinary keys held at once, with modifiers (Shift, Ctrl, Alt, Win/Cmd) counted in their own field beside it — that ordinary-key peak is your rollover in practice. If a key you are holding stays dark on the layout, that key is being blocked — note the combination, because the specific set is what matters, not the count.

A browser test has real limits, worth knowing before you blame the hardware:

The operating system takes some combinations first. Alt+Tab, the Windows or Command key, Ctrl+W, PrtSc and F11 may never reach the page. Test with letter keys, modifiers and Space for a clean reading.
Fn-layer keys are handled inside the keyboard and usually produce no event at all. Their absence is normal, not a fault.
Modifiers travel in a separate byte of the USB report, so they never occupy one of the six keycode slots. They still light up on the layout here, but they are kept out of the peak count and the rating: a 6KRO board holding Ctrl+Shift+Alt plus six letters is still 6KRO, not NKRO. Six letter keys is the real ceiling to look for.
Stopping at exactly six is the expected result for a healthy USB keyboard, not a defect. Many boards ship with an NKRO toggle — an Fn shortcut, the vendor software, or NK_TOGG in QMK/VIA.
This test cannot tell a matrix block from a dead switch. If one key never registers even on its own, that is a different fault — run the full keyboard tester to check each key individually.

Does gaming need NKRO?

For most games, no. Six keys plus modifiers is more than one hand realistically uses while the other is on a mouse; W, A, Shift, Space and R is already a lot of overlap in an FPS. What actually bites people is not the count but a cheap 2KRO board that cannot manage three keys at all, or an "anti-ghosting" board tuned for WASD when they play on ESDF.

NKRO earns its keep in a narrower set of cases: rhythm games where seven or more columns are held like a piano chord (osu! mania 7K is the classic example), stenography, MIDI input from a computer keyboard, fighting games played on keyboard, and MMO setups with dense keybinds. For those, NKRO is a requirement, not a nice-to-have. If you tap two or four keys as fast as possible instead of holding many at once, rollover is not your bottleneck — a keyboard cps test tells you more about that kind of input.

One thing NKRO does not do is make your keyboard faster. Rollover is about how many keys can be reported, not how quickly. Report rate is a separate property; if you want responsiveness rather than simultaneity, a keyboard polling rate test is the measurement you want. Buying NKRO to reduce input lag is buying the wrong feature.

Frequently asked questions

Why can't I press shift + space + W together?

Your keyboard is blocking that specific combination in its key matrix — those three keys share rows and columns the controller cannot resolve at once. It is a hardware limit, so no driver or software fixes it. Rebind one of the three to a key elsewhere on the board, or move jump to a mouse button, and the combination works again. A 6KRO or NKRO keyboard removes the problem permanently.

Is anti-ghosting the same as N-key rollover?

No. Anti-ghosting means the maker added diodes or extra wiring to a limited set of keys — usually the WASD cluster and modifiers — so common combinations do not block. N-key rollover means every key is isolated and no combination blocks at all. A board advertised as "19-key anti-ghosting" handles 19 particular keys, not any 19 you choose, which is why results change when you rebind away from WASD.

Do I really need NKRO for gaming?

For most games, no — 6KRO plus modifiers covers anything an FPS, MOBA or MMO asks of one hand. NKRO matters for rhythm games such as osu! mania 7K, stenography, MIDI input and keyboard-played fighting games. It also helps if you bind away from WASD, because budget "anti-ghosting" is usually tuned for the WASD cluster and stops protecting you on ESDF or the number row.

I can only press 6 keys at once — do I have to buy a new keyboard?

Not necessarily. Six keys plus modifiers is the standard USB boot-protocol report, so a perfectly healthy keyboard often stops exactly there. Many boards ship in 6KRO mode with an NKRO toggle hidden behind an Fn shortcut, the vendor's software, or NK_TOGG in QMK/VIA firmware — check that before replacing anything. If there is no toggle, six really is the ceiling and only different hardware raises it.

Why can't I press some keys at the same time when other combinations work fine?

Because blocking depends on which keys, not how many. The controller reads keys as row-and-column crossings, and when the pressed keys share enough rows and columns a fourth crossing completes that nobody touched. Rather than report a phantom key, the firmware drops one of the real ones. Keys spread across different rows and columns never collide, which is why Q+E+A fails while six scattered keys are fine.

Does converting a USB keyboard to PS/2 make it NKRO?

No. An adapter cannot add rollover the keyboard's controller never had, and you will typically end up capped at 6KRO or worse. PS/2 has the NKRO reputation because it sends an interrupt per key with no six-slot report limit, but the matrix still needs a diode behind every switch to take advantage of it. Only keyboards built for NKRO gain anything from the PS/2 port.

How many keys can my keyboard register at once?

Hold keys down one at a time on the test above and read the peak counter — that number is your answer, and modifiers are shown beside it rather than added to it, because they do not use up a keycode slot. Expect 2 on older membrane boards, 6 regular keys plus up to 8 modifiers on most USB keyboards, and no practical ceiling on NKRO boards. Manufacturers rarely print the figure on the box, and "anti-ghosting" on the spec sheet does not tell you the number, so testing beats reading.