Key rollover test
Hold down keys one after another without releasing. The page shows how many are down now, the maximum reached and which keys made up that maximum. When keys stop registering, you have found your keyboard's limit.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Click the page, then press and hold keys one by one.
- Keep adding keys until a new one makes no difference.
- Read Most keys at once and the list of keys at that maximum. Press Reset to repeat.
How it works
The page keeps the set of key codes currently down. A key repeat of a held key changes nothing, and releasing a key or switching away from the tab removes it. The maximum is the largest set size seen.
Worked example
Hold A, S and D: 3 keys, maximum 3. Release S, then hold F and G: A, D, F, G are down, so 4 now and the maximum becomes 4 with those four keys listed.
Tips
- Test gaming combinations such as W + A + Space + Shift to see if they register.
- Hold keys spread over the whole keyboard; some boards share circuits between nearby keys.
Frequently asked questions
What is key rollover?
It is how many keys a keyboard can report at the same time. N-key rollover (NKRO) means every key is registered together, while cheaper boards register only a few and may drop extra keys or produce ghost presses.
Why does my NKRO keyboard show only 6 or 10 keys?
USB boot-protocol keyboards report at most six keys plus modifiers. Some boards switch modes, and the operating system or browser can also limit what reaches the page, so the result is a floor for the whole chain, not only the keyboard.
Can I test just the keyboard?
Not with a browser alone. The number you see is what the keyboard, connection, system and browser pass on together. Try a different port or a wired connection to see if it changes.
Why do some keys never light up?
Special keys such as Fn and media keys are often handled by the keyboard or system and are never sent to web pages.