How to use the ghosting test
- Press a key and keep holding it.
- Add a second key, then a third, without letting go of the others.
- Watch the count and the drawing. When a key you add does not light up, you have found the limit for that combination.
The buttons above the drawing are combinations worth trying. Click one to outline its keys; it turns green once all of them are held at the same time. “Most at once” keeps your best result, and “ordinary keys” leaves out Shift, Ctrl, Alt and Win or Cmd, for the reason explained below.
Ghosting, blocking and rollover
Most keyboards wire their keys in a grid of rows and columns and scan it many times a second. When three keys at three corners of a rectangle in that grid are held, the key at the fourth corner can look pressed too. That phantom key is ghosting.
To avoid inventing keys, a keyboard without a diode behind every switch usually refuses the risky combination instead: the key you add simply does not register while the others are held. That is blocking, sometimes called jamming, and it is what most people mean when they say their keyboard ghosts.
Key rollover is how many keys a keyboard can report at the same time. “6KRO” means six keys, and “NKRO” (n-key rollover) means every key at once.
What the result tells you
- A key lights up that you are not pressing. That is true ghosting. It is rare on modern keyboards.
- A key you press does not light up while others are held. That is blocking. Press the same key on its own: if it works alone, the keyboard is fine and only limited in that combination.
- The count of ordinary keys stops at six. The keyboard is using the basic keyboard report from the USB HID specification, which has room for six keys plus the eight modifiers (left and right Shift, Ctrl, Alt and Win or Cmd). Many gaming keyboards can switch to NKRO in their software or with a key combination; the manual will say how.
- More than six ordinary keys register. The keyboard reports beyond that basic format, so it will not be the limit in games.
Which combinations matter
Typing rarely needs more than two or three keys at once, because fast typists roll from one key to the next. Games are different: moving diagonally while jumping and sprinting holds W and A (or D), Space and Shift together, which is exactly where cheaper keyboards block. That is why those combinations are offered above. Rhythm games and stenography need the most, and are where NKRO really counts.
The home row combination, A S D F J K L and the semicolon, is eight ordinary keys. A keyboard limited to six cannot pass it, which makes it a quick way to tell 6KRO from NKRO.
Limits of a browser test
The page sees the same key reports that other programs on your computer receive, so what fails here will fail in a game too. Two things are worth knowing:
- On a Mac, keys pressed while Command is held only flash and are not counted, because macOS does not report when they are released.
- If the page loses focus, for example when a system shortcut opens something else, every held key is cleared, because the releases no longer reach the page. Click the page and start again.
To check that every key works on its own first, use the keyboard test. For a key that types twice, use the keyboard double typing test.