Key Rollover & NKRO Test
Hold down several keys at once. The on-screen keyboard lights up every key that registers, so you can see your rollover limit and catch ghosting.
Hold down several keys at once. Keys that register light up teal. If some keys refuse to light while others are held, your keyboard has reached its rollover limit (ghosting).
What Is Key Rollover and Why Does It Matter?
Key rollover describes a keyboard's ability to correctly register multiple keys pressed simultaneously. When a keyboard has high or full key rollover, pressing many keys at once results in every key being correctly identified and reported to the operating system. When rollover is limited, some keystrokes are dropped, misreported, or prevented from registering at all.
This matters most to gamers, programmers, and fast typists who routinely press several keys in rapid succession or simultaneously. In competitive gaming, actions like sprinting (Shift), moving forward (W), and crouching (Ctrl) might all need to be held together while another key triggers an ability.
NKRO vs. 6KRO: Understanding the Difference
The two standards most often discussed in keyboard specifications are 6KRO (six-key rollover) and NKRO (n-key rollover, where N means any number). A 6KRO keyboard can correctly register up to 6 non-modifier keys pressed simultaneously plus modifier keys such as Shift, Ctrl, and Alt. In the majority of real-world gaming and typing scenarios, 6KRO is adequate.
NKRO keyboards report every single key independently regardless of how many are pressed at once. True NKRO is particularly valued in rhythm gaming, where hand positions can require pressing many keys simultaneously.
What Is Keyboard Ghosting?
Ghosting is the related but distinct problem of a keyboard registering keys that were never pressed. It occurs in traditional matrix-wired keyboards when a specific combination of simultaneously pressed keys creates an electrical path through the circuit that mimics a fourth key being pressed.
Anti-ghosting technology addresses this by adding diodes to the keyboard circuit so that current can only flow in one direction, breaking the phantom electrical paths. A keyboard marketed as anti-ghosting prevents phantom keystrokes from appearing. Mechanical keyboards commonly include both anti-ghosting and high rollover.
How to Use the Key Rollover Test
Open the test tool and begin pressing keys while watching the on-screen keyboard visualization. Each key that is correctly registered will be highlighted. Start by pressing 2 keys simultaneously, then add a third, fourth, and fifth. Note the point, if any, at which a key you pressed fails to appear highlighted or a key you did not press becomes highlighted.
For a systematic test, use a row of adjacent keys like ASDFGH since these are common in gaming hand positions. Then test modifier combinations by holding Shift or Ctrl while adding letter keys. If you only need to confirm that individual keys work one at a time, the keyboard tester covers that. For response time rather than rollover, the keyboard latency test measures how fast each press registers, and the keyboard CPS test measures repetition speed.
Frequently Asked Questions
What does NKRO mean on a keyboard?
NKRO stands for n-key rollover, where "n" represents any number. An NKRO keyboard can register every key pressed simultaneously without dropping or misidentifying any inputs.
Is 6KRO enough for gaming?
For the vast majority of games, yes. Most gaming actions require 3 to 5 simultaneous key inputs at most. NKRO becomes relevant for rhythm games or highly complex multi-key binds.
What is the difference between anti-ghosting and NKRO?
Anti-ghosting prevents the keyboard from registering keys that were not actually pressed. NKRO describes how many real simultaneous keypresses can be correctly registered. A keyboard can have anti-ghosting with limited rollover, or NKRO without the ghosting problem being discussed separately.
Why do some gaming keyboards need a special mode to enable NKRO?
The standard USB HID keyboard protocol only supports up to 6 simultaneous non-modifier key reports. NKRO over USB requires a custom HID report format, which some keyboards enable through a separate firmware mode.
Can the key rollover test work on wireless keyboards?
Yes. The test runs in the browser and receives keyboard input the same way regardless of whether the keyboard is wired or wireless.