Keyboard ghosting and N-key rollover (NKRO) explained
Updated August 2026 · TapTest guides
Press the right combination of keys on some keyboards and one of them simply will not register. That is ghosting, and here is what is going on.
Hold down a few keys at once on a cheaper keyboard and you may notice one of them stops registering, or a key you never pressed appears. This is ghosting, and it comes down to how keyboards are wired. Here is the plain-English version.
What is ghosting?
Ghosting is when a keyboard fails to register a key because too many others are held at the same time. In the classic case, it registers a "ghost" key you did not press. On most keyboards it shows up as certain three-or-more key combinations simply not working.
Why it happens
Keys are not each wired individually. They sit on a grid (a matrix) of rows and columns to keep the wiring simple and cheap. When you press a key, the keyboard reads which row and column crossed. Press several keys that share rows and columns and the controller can no longer tell which combination you meant, so it drops or invents a signal. That is the root cause of ghosting.
Rollover: 2KRO, 6KRO and NKRO
Rollover is how many keys a keyboard can register at once. You will see it written as a number:
- 2KRO: guarantees any two keys plus modifiers. Fine for typing, limiting for games.
- 6KRO: registers six normal keys at once (plus modifiers like Shift and Ctrl). This is the common standard, partly because of a limit in the older USB keyboard specification.
- NKRO: N-key rollover, meaning every key can be pressed and registered simultaneously with no limit. This is what enthusiast and gaming keyboards advertise.
Anti-ghosting vs true NKRO
These two terms get mixed up. "Anti-ghosting" usually means the maker has wired the most important keys (often the WASD cluster and its neighbours) so they will not ghost, while the rest of the board is still limited. True NKRO means the whole board is diode-isolated so any combination works. If it matters to you, look for the specific claim "full NKRO" rather than just "anti-ghosting". Note that full NKRO often needs a USB connection and, on some boards, a mode toggle.
Why it matters
For everyday typing, 6KRO is plenty, since you rarely hold six keys at once on purpose. For gaming it matters more: sprinting diagonally while reloading and crouching can easily be four or five simultaneous keys, and on a ghosting-prone board one of those inputs will silently fail.
How to test your keyboard
You can measure your own board in seconds. Open the keyboard tester and hold down as many keys as you can at once. Try a realistic gaming grip like W, A, Shift, Ctrl and Space together. Watch the "Held now" counter: it shows exactly how many keys are registering simultaneously. If you can hold six and a seventh refuses to appear, you have a 6KRO board; if they all keep counting up, you have full NKRO. It is the simplest way to know what your keyboard can really do.