Anti-Ghosting & NKRO Tester
Hold as many keys as you can at once. Highlighted keys are the ones your keyboard actually reported. Focus this page first, then press.
How it works
仕組みAnti-ghosting and N-key rollover (NKRO) describe how many keys a keyboard can register at the exact same moment. Cheaper membrane boards drop or invent keypresses once you hold several keys in the same wiring zone. Press keys below and watch which light up; the counter tracks the most you registered at once.
Ghosting is when a keyboard fails to report a key you're physically holding, because its matrix can't distinguish certain simultaneous combinations. Here it shows up as a key that simply never lights while others are held.
Most USB keyboards guarantee 6-key rollover (6KRO) plus modifiers. Full NKRO reports every key independently. If your max tops out around six, that's normal for many boards.
It depends on your specific keyboard talking to your browser right now. There's no lookup table; only your own hardware can answer.