An N-key rollover in a keyboard means each key press in the keyboard will be registered individually when a number of keys are pressed simultaneously. If a keyboard comes with n-key rollover, it means it can scan each key press individually, implying that even if you press a lot of keys at the same time, each key press will give some output.
The ‘N’ in the N-key rollover stands for the number of keys that come with this function. Suppose a keyboard has a 6-key rollover (6KRO), then six keys can be pressed simultaneously for the input. Some cheaper keyboards have 3-key rollover (3KRO) also.
Pressing several keys at the same time finds a lot of use in gaming. And as such, not every keyboard comes with an n-key rollover as the inclusion of the tech ramps up the production costs.
Pressing more keys than are allowed in the N-key rollover
Suppose your keyboard is 3KRO, then if you press four keys at the same time, the fourth unassigned key may be blocked or jammed and you may not see any input from that. Another issue could be that of ghosting, which means you might see some input from a key you never pressed only.
Should you be worried about the N-key rollover feature?
Not at all if you are going to buy a keyboard for regular purposes and do not intend to use it to learn and practice advanced typing tricks or do some serious gaming. But if you are specifically buying a keyboard for gaming, then you might need to press a number of keys at the same time to trigger some special moves in the game and that could give you an edge over the opponent.
Let’s say you are holding down the Shift key while switching between the W,A and D buttons to run in an unpredictable manner. Now if you have to jump, you’ll have to press Space also while holding the previous two keys. You are ready to do that but see an enemy on the opposite side of a structure or ramp, you might want to press another designated key to trigger the kill move. But if there is just the 3-key rollover, the fourth key will not get registered and hence, game over for you. So, this feature in a keyboard is usually best suited for serious gamers.