N-Key Rollover Test Page

Use this page to test your keyboards N-Key Rollover


Using This Demonstration
Click on the keyboard shown below. It will then show what keys are being pressed on your keyboard (or to be more specific, the ones that are being passed to your web browser). You can use this to see if there are certain key combinations that fail to work correctly.




If you prefer a more fool proof method of testing your N-Key Rollover, AquaKeyTest is a Windows based program that installs locally and listens to the output your keyboard is actually sending to the computer. This program can also be used to test every key on your keyboard, and is not faked out by scripts or any hotkey shortcuts or macros that may be on the keyboard.


How To Hunt For Ghosts
Ghosts can be somewhat elusive. Just because you find some combination of 6 keys that reports correctly does not necessarily mean that every combination of 6 works. In fact, the most straightforward keyboard design has thousands of 3-key combinations that do not work! That is a lot, but it is still less than 5% of the total number of 3-key combinations.
A quick way to find problematic combinations is to press and hold ASDW (the most popular keys for moving around in games), and then while holding those down, press every other key in turn. If you find a key that does not work, try releasing some of the ASDW keys. Odds are high that you will find a 3-key combination that fails.


  1. Peter June 12, 2013 5:13 am  Reply

    I love this little test. It's great watching keypresses in real time. But, I'm not sure about the N-key Rollover.

    I am using a Filco Tenkeyless MX Black mechanical keyboard. I came with USB as standard and the purple PS/2 adapter to plug into the 'legacy' PS/2 port on the mobo.

    I wasn't happy with that so I modded it out to a dedicated PS/2 connection on the mobo instead of PS/2 by adapter.

    I feel it works better. More direct some how. I can't really explain the difference but it feels more snappy it that makes sense.

    Just my two bits.

    Also, is that your own keyboard demo? It's pretty nifty. It's just that I type in Colemak, so whilst the keys are they same, they are 'displayed' as QWERTY. I was just wondering if you could adapt the code to reflect a Colemak etc layout?


  2. G.G. Campbell December 23, 2013 2:09 am  Reply

    Very slick.
    Any chance of seeing the source and how you did this?
    I wanted to capture the n-key rollover stuff in javascript.

    • CubedRoot December 27, 2013 10:18 am  Reply

      Sorry, unfortunately the source is not available.

  3. Cawston September 2, 2014 5:22 pm  Reply

    so i have a six key rollover for typing and a setting for gaming that allows me to hold down every key at once what is the advantage to having a six key rollover compare to the n key function why not just default to the nkey and leave the button out?

    • Richard Oliver Barrell October 16, 2014 1:53 pm  Reply

      Cawston: 6-key is a limitation of the USB human-interface-device standard. A lot of gaming keyboards can understand n keys, but can only send up to 6 when connected via USB unless using a non-standard protocol requiring a driver specific to that keyboard.

Leave a Reply