Keyboard Ghosting Test: Check N-Key Rollover in Your Browser

You hold W and A to move diagonally, press Shift to run and Space to jump, and nothing happens. The keys are not broken. The keyboard simply could not report that combination. That is ghosting, and it is a property of the keyboard, not a fault in one key. A keyboard ghosting test in the browser shows which combinations yours drops, in about a minute.

Why keyboards drop keys

A keyboard does not have one wire per key. The keys sit on a grid of rows and columns, and the controller scans the grid to see where a row and column meet. With two keys held, that works. With three held in a certain pattern, the current can find a path through them that looks like a fourth key. A basic keyboard then has two choices: report a key you did not press, which is true ghosting, or refuse to report the extra key, which is called blocking or jamming.

Almost every keyboard made today blocks rather than ghosts, so in practice “ghosting” means “a key I pressed did not register”. Better keyboards add a diode to every switch, which stops current from flowing backwards and lets the controller read any combination.

What the rollover numbers mean

Label	Keys reported at once	Where you find it
2KRO	2, plus modifiers	Cheap office and many laptop keyboards
Partial or “anti-ghosting”	Some combinations of 3 to 5	Budget gaming boards, often only in the WASD area
6KRO	6, plus modifiers	Most USB keyboards in their standard mode
NKRO	Every key	Mechanical and gaming keyboards with a diode per switch

Modifiers such as Shift, Ctrl, Alt and the Windows or Command key are reported separately in the standard USB mode, so they usually do not count against the six.

“Anti-ghosting” on a box is a loose term. It often means the maker tested a few popular gaming combinations, not that every combination works.

How many keys do you need?

Typing: two or three. Even fast typists rarely hold more than that at once.
Most games: four to six. Movement, a modifier, and one or two action keys.
Rhythm games and stenography: more than six, and here NKRO matters.
Two players on one keyboard: more than six, because two sets of keys are held at the same time.

Keyboard ghosting test: how to check yours

Open the keyboard test and select the Rollover tab. Hold down one key, then add a second without letting go, then a third, and keep going. The page shows the highest number of keys it saw held at the same time.

Test the combinations you actually use, not random keys. Hold W, A and Shift, then add Space, then add E. If the count stops rising when you add a key, that combination is blocked. Try the same number of keys in a different area of the board: many keyboards handle the WASD cluster better than the rest.

Read the number as a floor. A browser only sees what the operating system passes on, and some keyboards only switch to full NKRO in a special mode. If the box promises NKRO and you see six, look in the manual for a mode switch or a key combination that turns it on.

What a rollover result means

6 or more: fine for almost every game. You are unlikely to run into a limit.
3 to 5: some combinations will drop. Remap the keys that fail in the game’s settings, or move them to keys that sit in a different part of the grid.
2: an office keyboard. Fine for typing, frustrating for gaming.

Rollover cannot be repaired. It comes from how the keyboard is wired, so cleaning does nothing for it. If your count is low and it matters to you, the fix is a keyboard with a diode per switch, which is standard on most mechanical boards.

Ghosting is not chatter

A key that types twice from one press is a different fault, called chatter, and it comes from a worn or dirty switch. A key that never registers at all, even alone, is a dead key. Both have their own fixes, covered in keyboard keys not working or typing twice. The gaming keyboard test runs the same checks with tips for game controls.

If you are testing a whole setup, the mouse test checks buttons and the scroll wheel in the same two minutes.

Questions people ask

How do I do a keyboard ghosting test?

Open a rollover test, such as the Rollover tab of the keyboard test here, and hold down the keys you use together one at a time. If the count stops rising when you add a key, that combination ghosts. It runs in the browser, with nothing to install.

What is keyboard ghosting?

Ghosting is when a keyboard cannot report a key press because other keys are already held down, so the press is dropped. It happens with specific combinations, which is why it shows up in games where three or four keys are held together.

What is the difference between 6KRO and NKRO?

A 6KRO keyboard reports up to six ordinary keys at once, plus modifiers such as Shift and Ctrl. An NKRO keyboard reports every key at once. For typing and almost every game, six is enough; NKRO matters mostly for rhythm games and stenography.

Can a browser test show NKRO?

A browser test shows the most keys it saw at once, which is a floor rather than the keyboard's true limit. Some keyboards only report more than six keys in a special mode, and the operating system and browser can cap the count too.

Can ghosting be fixed?

Not with cleaning or settings. Rollover is part of how the keyboard's circuit is wired. Some gaming keyboards have an NKRO switch or a software setting, so check the manual; otherwise the answer is a keyboard with better rollover.

Keyboard ghosting test: what ghosting and n-key rollover mean, and how to check yours

The short answer