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N-Key Rollover Test — Count Keys Registered at Once

Hold down as many keys as you can and see the highest number your keyboard reports together. That number tells you whether you have 2KRO, 6KRO or full NKRO.

N-Key Rollover Rating

Not Tested

Press multiple keys at once to test rollover.

Max simultaneous keys0

02KRO6KROFull NKRO (10+)

Currently pressing: 0 key(s)

What the rollover number means, and why six is such a common answer

N-key rollover describes how many keys a keyboard can report as held at the same time. The N is a variable: full NKRO means there is no limit, and every key on the board can be down at once and correctly accounted for. A keyboard with 2KRO manages two, 6KRO manages six. The number above is the highest count this page has seen from your keyboard, which is the practical version of that specification.

If your result is exactly six, that is almost certainly not your keyboard's limit. It is the USB HID boot protocol. The standard report is eight bytes: one for modifier bits, one reserved, and six for keycodes. Six slots, so six keys, no matter how capable the hardware underneath is. Boards ship in this mode because it is what a BIOS or UEFI firmware understands — you need the keyboard to work before any driver has loaded — and many of them have an NKRO mode that simply has to be switched on.

The escape from six comes in two shapes. Some keyboards send a bitmap report with one bit per keycode, so any combination can be expressed at once. Others present themselves as several six-key keyboards on separate USB endpoints and spread the load across them. Both reach the same result; the bitmap approach is cleaner but is the one more likely to fail in a BIOS, which is why boards that use it usually keep 6KRO as a fallback mode. A historical footnote worth knowing: PS/2 keyboards were inherently unlimited, because they streamed individual scancodes rather than filling a fixed-size report. USB traded that away for plug-and-play.

One thing to be deliberate about while testing: hold letters and numbers, not modifiers. Shift, Control, Alt and the Windows or Command key travel in their own byte of the HID report and are not subject to the six-key cap at all. Four modifiers plus six letters reports as ten keys and looks like full NKRO when it is ordinary 6KRO doing exactly what the spec says. This page counts everything the browser reports, so the honest test is ten fingers flat on the home row.

This test gives you one number. If you want to know which combinations break rather than how many keys survive, the ghosting test is the right tool — a board can have a respectable ceiling and still drop keys in one awkward corner of the matrix, and that corner is what ruins a game.

Key Capabilities & Features

Peak Count Held

Records the highest number of simultaneous keys seen across the session, so one good attempt is enough.

Graded Against Real Tiers

Places your result on the scale that actually exists in hardware: 2KRO, 6KRO and full NKRO.

Live Key Listing

Names every key currently down, so you can see which one stopped reporting when the count froze.

Detects the 6-Key Wall

A result of exactly six is the HID boot protocol rather than your keyboard, and that distinction is the one worth acting on.

Reads Events As Delivered

Uses the browser key events the operating system provides, with no driver or vendor software in the path.

Nothing Installed

Runs entirely in the page. No keystroke is stored or transmitted.

How to Perform This Test

Two-key baseline: press F and J together. Every keyboard ever made manages this, so it confirms the test is reading your input.
Six-key threshold: hold Q, W, E, A, S and D at once. If the count reaches six and refuses to go higher, note it — the next step tells you whether that is the protocol or the hardware.
Add a seventh: keeping those six down, press R. If the count sticks at six you have found your wall; if it moves to seven, your board is already past the boot-protocol limit.
Ten-finger slam: lay both hands flat across the home row — A S D F G H J K L and semicolon — and press down together. This is the honest full-NKRO test.
Use letters, not modifiers: modifiers are reported in their own byte and do not count against the six-key cap, so including them inflates the result.
Read the grade: the peak count and its tier stay on screen until you reset, so you can compare two keyboards back to back.

Troubleshooting Common Hardware Issues

Stuck at exactly 6: this is the HID boot protocol, not a hardware limit. Look for an NKRO toggle — Fn + N is the most common, some boards use Fn + Shift + N or a DIP switch underneath, and QMK firmware has a built-in NKRO toggle. Vendor software often exposes it as a "full key rollover" or "6KRO / NKRO" option.
Stuck at 2 or 3: this is the matrix. The board lacks per-switch diodes and no firmware setting will change it. Common and normal on bundled office keyboards.
Full NKRO in Windows but only 6 keys in the BIOS: expected behaviour. Bitmap NKRO reports are not part of the boot protocol, so a board in that mode falls back to six keys before the operating system loads. If your BIOS will not accept the keyboard at all, switch it to 6KRO temporarily.
Wireless drops to 6 keys: many keyboards deliver full NKRO over USB and over their own 2.4 GHz dongle, but fall back to 6KRO in Bluetooth mode. Plug the cable in and retest before concluding anything about the hardware.
Plug directly into the machine: unpowered hubs, KVM switches and long extension cables can impose their own limits, and a marginal connection looks exactly like a matrix fault.
Very large slams can trip operating system shortcuts: twenty keys at once may hit something the OS claims before the browser sees it. Testing up to twelve or fourteen keys is enough to establish full NKRO.

The rollover tiers, and who needs which

Tier	Keys at once	Why it stops there	Enough for
2KRO	2	No diode isolation. The matrix cannot resolve a third simultaneous key.	Typing, browsing, office work
6KRO	6 plus modifiers	The USB HID boot report has exactly six keycode slots.	Almost all gaming, all typing
Full NKRO	Every key	Per-switch diodes plus a bitmap or multi-endpoint report.	Rhythm games, stenography, music input

Is full NKRO actually worth paying for?

For typing, no. Even at a high words-per-minute rate you overlap two or three keys, and one of those is usually a modifier that does not count toward the cap. 6KRO has never been the thing slowing a typist down.

For most gaming, also no — but the reason is worth stating precisely. Game control schemes rarely exceed six simultaneous non-modifier keys, so 6KRO is genuinely sufficient. What actually causes dropped inputs in games is not the ceiling but matrix blocking in a specific cluster. A board advertised as anti-ghosting may protect WASD and leave the rest of the keyboard without diode isolation, which shows up as a key dying in one particular combination while the headline count stays high. That is why the two tests answer different questions.

Where full NKRO earns its price is inputs that are chords by design. Stenography software expects whole words to land as one simultaneous press, and Plover effectively requires NKRO to work at all. Rhythm games at high difficulty overlap more keys than six. Music software mapping a keyboard to notes needs every voice held. In those three cases it is a requirement rather than a specification bullet.

Practical advice: if your result is six, try to enable NKRO before spending money — it costs nothing and often works. If your result is two or three and you play anything, that is the one case where a new keyboard genuinely fixes something. Either way, check the gaming keyboard test for the clusters that break during play, since a good number here does not guarantee a good result there.

Frequently Asked Questions

What is N-key rollover?

It is the number of keys a keyboard can report as held simultaneously without dropping any. The N is a variable — full NKRO means there is no limit and every key on the board can be down at once. Achieving it needs two things: a diode on each switch so the matrix can resolve any combination, and a USB report format that can express more than six keys.

Why does my keyboard stop at exactly 6 keys?

That is the USB HID boot protocol rather than your keyboard. Its report is eight bytes — one for modifier bits, one reserved, and six for keycodes — so six keys is all it can express. Keyboards ship in this mode because it is what a BIOS understands before any driver loads. Many have an NKRO mode you can switch on, commonly with Fn + N or in the vendor software.

What is the difference between 2KRO, 6KRO and NKRO?

2KRO reports two simultaneous keys and means the board has no diode isolation — a hardware limit that cannot be changed. 6KRO reports six plus modifiers and is almost always the USB protocol rather than the hardware. NKRO reports as many keys as you can physically hold. The jump from 2 to 6 requires different hardware; the jump from 6 to N is often just a setting.

Do I need NKRO for gaming?

Usually not. Game control schemes rarely need more than six simultaneous non-modifier keys, so 6KRO covers essentially all of them. Dropped inputs in games are more often matrix blocking in one cluster than a ceiling problem — which is what the ghosting test is for. NKRO is a genuine requirement for stenography, high-level rhythm games and music input, where many keys land together by design.

How do keyboards achieve full NKRO?

Two parts. Physically, a diode in series with every switch stops the phantom current paths that make three simultaneous presses ambiguous. In firmware, the keyboard either sends a bitmap report with one bit per keycode, or presents itself as several six-key keyboards on separate USB endpoints and spreads keys across them. Both work; the bitmap approach is cleaner but less likely to be understood by a BIOS.

Why do I get a high count when holding modifiers?

Because modifiers do not count against the six-key limit. Shift, Control, Alt and the Windows or Command key are reported as bits in their own byte of the HID report, entirely separately from the six keycode slots. Holding four modifiers plus six letters legitimately reports ten keys on an ordinary 6KRO board. Test with letters and numbers only if you want a meaningful number.

Does NKRO work over Bluetooth?

Sometimes, and it is worth checking rather than assuming. Many keyboards deliver full NKRO over USB and over their own 2.4 GHz dongle but fall back to 6KRO in Bluetooth mode. If your wireless result is six and your wired result is higher, that is the reason, and it is a firmware decision rather than a fault.

Can NKRO be added with a driver or software?

The reporting half sometimes, the hardware half never. If your keyboard has an NKRO mode, firmware or vendor software can switch it on and genuinely lift you from six keys to unlimited. But if the circuit board lacks per-switch diodes, the matrix physically cannot tell which keys are pressed, and no software can supply information that never arrived.

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