Mechanical Keyboard Tester — Test Keys Online

Switch chattering happens when a worn or faulty spring causes the metal contacts to bounce as the key is released — momentarily opening and closing the circuit, registering two keydown events from one physical press. In the tester, a chattering key will flash twice rapidly for a single press. It is most common in high-actuation-count switches (50M+ presses) and in budget switches with inconsistent spring weights. Chattering cannot be fixed by cleaning — the switch needs to be replaced or hot-swapped if your keyboard supports it.

Hold down as many keys as possible at once and watch the Keys Held Now counter. NKRO keyboards will continue counting regardless of how many keys you hold. 6KRO keyboards will stop at 6. Note: many keyboards that advertise NKRO over PS/2 drop to 6KRO over USB due to USB protocol limitations. Test with your actual connection method (USB vs. PS/2) to see your real rollover.

Phantom key inputs from a mechanical keyboard are usually caused by: (1) a stuck switch — debris or a failed spring holding the contact closed, making the key appear always-pressed; (2) switch actuation from nearby vibration — linear switches with very low actuation force (25–35g) can register from impact on the desk; or (3) switch oxidation on a rarely-used key — the contact surface develops a thin oxide layer causing intermittent false triggering. Clean the switch contact with isopropyl alcohol or replace the switch.

No — N-key rollover is determined by the keyboard's PCB and firmware design, not the individual switch type. A keyboard with Cherry MX Red switches and one with Cherry MX Blue switches on the same PCB will have identical rollover. What switch type does affect is actuation force, tactile feedback, noise level, and actuation distance — none of which influence how many simultaneous keys the keyboard can register.

After installing new switches, use this tester to verify each replaced switch registers correctly. Press the new switch and confirm it lights up. Also test for chattering (each press should register exactly once) by tapping the key rapidly and watching whether it double-fires. Hot-swap sockets occasionally have bent pins that prevent a new switch from making full contact — these will show as non-registering keys in the tester.

6KRO (6-key rollover) means the keyboard can register exactly 6 standard keys pressed simultaneously, plus modifier keys (Shift, Ctrl, Alt, Win) which are counted separately. Full NKRO means every key on the keyboard can be pressed simultaneously with no drops. For gaming, 6KRO is sufficient for virtually all scenarios — competitive games rarely require more than 5 simultaneous inputs. NKRO matters most for professional fast typists and specific rhythm game inputs requiring 6+ simultaneous presses.