Key Rollover Test — NKRO & Ghosting Check
Press any key and watch it light up on an on-screen keyboard: check every switch, count simultaneous keys and spot dead or chattering keys.
Processed entirely in your browser — nothing you enter here is ever uploaded.
Result
About this tool
This page opens the keyboard tester with the simultaneous-keys counter highlighted: hold down more and more keys and watch how many actually register at once — the maximum reached stays on screen.
Rollover is how many keys a keyboard can report at the same time. Budget boards often manage only a few keys in some combinations and may "ghost" — register a key you never pressed — while gaming keyboards advertise 6-key rollover (6KRO) or full N-key rollover (NKRO). Try classic problem clusters like WASD plus Space and Shift.
One honest caveat: the browser and the operating system can cap how many simultaneous keys they pass through, especially in some USB modes. A low reading here proves nothing by itself — but a high one confirms your board, cable and OS all handle the combination fine.
Example. Pressing the A key lights that key and appends its code to the press history, while a held key does not add extra counts because auto-repeat events are ignored.
Limit. The history line keeps only the latest 24 presses, and Tab, Space, quote, backtick, and F1 through F12 are swallowed so the page does not follow them.