Keyboard Ghosting & Rollover Test
Find out how many keys your keyboard can register at once. Hold down as many as you can: if the count stops rising at six plus modifiers, your keyboard is limited to 6-key rollover rather than full NKRO.
Hold several keys together — try WASD plus Shift and Space, the combination games use most.
Rollover is how many keys a keyboard can report simultaneously; ghosting is when a held combination causes a key to be silently dropped because the wiring matrix cannot distinguish it. N-key rollover (NKRO) means every combination registers correctly, with no practical limit.
How to use this test
- Click the panel above so the page has keyboard focus.
- Hold down two keys, then three, then four, adding keys without releasing the ones you are already holding.
- Watch the 'keys held now' figure. When it stops rising as you add keys, you have found the limit for that combination.
- Try the combinations you actually use — WASD with Shift and Space for games, or your common modifier chords.
What your results mean
| What you see | What it means |
|---|---|
| The count keeps rising past six | Your keyboard handles a high number of simultaneous keys, and is likely advertised as N-key rollover. |
| The count stops at six (plus modifiers) | Standard USB boot-protocol behaviour, and completely normal. Six keys plus modifiers is more than most typing or gaming needs. |
| The count stops at two or three | A rollover limit typical of cheaper membrane keyboards. Not a fault, but it can drop inputs in games. |
| A specific combination drops a key while others work fine | Classic ghosting. The keyboard's wiring matrix cannot distinguish that particular set, so it suppresses one to avoid reporting a key you did not press. |
Common problems and fixes
Keys stop registering in games but typing is fine
Typing rarely holds more than two keys at once, so a rollover limit stays invisible until you hold movement keys plus a modifier. Test the exact combination your game uses.
The browser intercepts some combinations
Certain keys are reserved by the browser or the operating system and never reach the page. Tab is excluded here for accessibility. Combinations involving the OS key are often captured before any page sees them.
Your keyboard claims NKRO but tests low
Some keyboards ship in a compatibility mode and need a switch — often a key combination or a setting in the manufacturer's software — to enable full NKRO. Check the manual.
The result differs between USB and Bluetooth
That is expected. Wireless protocols often report fewer simultaneous keys than the same keyboard does over USB.
Why this matters
Rollover limits are invisible until the moment they matter, and then they read as your own mistake — a character that would not strafe while jumping, a shortcut that would not fire. Knowing your keyboard's real limit tells you whether to remap a binding or replace the board, and it settles whether an advertised NKRO feature is actually switched on.
Longer walkthrough: Keyboard Ghosting Test — full guide.
Rollover in numbers
6-key rollover (6KRO) means six simultaneous keys plus modifiers — the limit of the USB HID boot protocol, and what most membrane keyboards report.
N-key rollover (NKRO) means every key can register at once, and requires the keyboard to use a different USB reporting mode.
Browsers add their own ceiling: some key combinations are reserved by the operating system and never reach a web page, so a browser test measures the practical limit rather than the theoretical one.
Frequently asked questions
What is keyboard ghosting?
Ghosting is when pressing several keys at once causes one of them not to register. The keyboard's key matrix cannot distinguish certain combinations, so rather than report a key you did not press, the controller suppresses one you did. It is a design limitation, not a defect.
What does N-key rollover mean?
NKRO means every key is wired so that any combination of simultaneous presses registers correctly, with no practical limit. It is achieved by giving each key its own electrical path, usually with a diode, so no combination is ambiguous.
Why do many keyboards stop at six keys?
Because the standard USB keyboard boot protocol reports six keys plus modifiers, which is what guarantees a keyboard works in a BIOS or before drivers load. Keyboards supporting more usually switch to a different reporting mode once the operating system is running.
Is six-key rollover enough for gaming?
For most games, yes. Typical movement uses three or four keys plus a modifier or two, which fits comfortably. It becomes a problem in games needing many simultaneous inputs, or with unusual binding layouts.
Can ghosting be fixed in software?
No. It is determined by the keyboard's physical wiring matrix. Software can remap keys to avoid a problematic combination, but it cannot make the keyboard report a combination the hardware cannot distinguish.
Why does the test miss keys I definitely pressed?
Either your keyboard has reached its rollover limit, which is the result the test is looking for, or the browser or operating system intercepted the combination before the page received it. System-level shortcuts are the usual second cause.
Sources: MDN — KeyboardEvent.code · MDN — KeyboardEvent.key
Found an error on this page, or a result that does not match your hardware? Tell us and we will correct it.