How to Run a Keyboard Rollover Test
Our online keyboard tester maps inputs in real time to diagnose key responsiveness, dead switches, and rollover limits. To execute a test, follow these steps:
- Press and Hold Keys: Press keys individually to verify they light up in green (active) and remain highlighted in purple (registered/safe) after release. This ensures every individual dome or switch contact functions perfectly.
- Perform Chord Tests: Hold down multiple gaming keys simultaneously (for example, W + A + S + D + Shift + Space). Verify if all keys highlight green together.
- Reboot/Reset: Click "Reset Map" to clear registered key states and begin a clean test.
What is N-Key Rollover (NKRO) vs. 6-Key Rollover (6KRO)?
**Rollover** defines how many simultaneous key presses a keyboard can register accurately:
- 6-Key Rollover (6KRO): Standard USB office keyboards can register a maximum of six character inputs plus modifier keys (Ctrl, Alt, Shift) at once. If you press a seventh key, it will be ignored (blocked).
- N-Key Rollover (NKRO): High-performance mechanical gaming keyboards feature full NKRO. This means every single key on the keyboard can be pressed down simultaneously, and the system will register all of them independently.
**Ghosting** and **blocking** are side effects of cheap keyboard circuitry. In a membrane keyboard matrix, keys share electrical lines. If you press three keys that form a grid intersect, the controller gets confused. It might either block your input (unregistered press) or register a "ghost" key that you didn't touch, causing fatal errors in games.
Mechanical Switch Debounce Delay and Key Chattering
Mechanical keyboard switches contain physical metal leaves that touch when pressed. However, because metal is elastic, the contacts bounce against each other rapidly (chatter) before settling down, which takes about 1ms to 5ms. Keyboard firmware uses a **debounce delay** algorithm to ignore these bounces and avoid double-character inputs. As switches age or accumulate dust/oxidation, the chatter duration exceeds the debounce window, leading to double-typing ("key chattering"). If you experience keys double-registering or completely failing on single clicks, it indicates switch degradation.
KEYBOARD NKRO & ROLLOVER FAQ
How do I know if my keyboard has full NKRO?
Lay both hands flat across your keyboard and press as many keys as possible (at least 10–15 keys). If our tester highlights every single key you are holding in green, your keyboard has N-Key Rollover. If it caps out at exactly six registered keys, your keyboard is limited to 6KRO.
What is keyboard ghosting?
Keyboard ghosting is when a key you didn't physically press registers as active. In modern keyboards, true "ghosting" is rare because manufacturers use diodes to isolate key switches. Instead, cheap keyboards suffer from "blocking," where pressing certain key combinations prevents additional keys from registering.
Why do some keys ignore inputs when other keys are held down?
This is due to hardware blocking limits on membrane keyboards. To save costs, columns and rows in the circuit board share pathways. When certain key patterns are pressed (e.g. W + Shift + Space), the controller blocks other keys on the same shared line to prevent ghosting inputs, causing key failures in games.
Can I fix keys that double-type or fail intermittently?
Yes. For hot-swappable keyboards, you can swap the switches with new ones easily. If it is soldered, you can drop a few drops of 99% Isopropyl Alcohol directly inside the switch stem, press it repeatedly to clear out dust/grime, or replace the switch using a soldering iron.