Keyboard Ghosting & NKRO Test
Test your keyboard for ghosting and N-Key Rollover with a live virtual keyboard, simultaneous keypress tracking, guided gaming-combo stress tests, and a millisecond-precision key log.
Desktop Hardware Required
This tool requires a physical keyboard/mouse to measure metrics accurately, so it isn't available on mobile or touch devices. Try one of these mobile-friendly tools instead:
Gaming Combo Stress Test
# Keyboard Ghosting & N-Key Rollover (NKRO) Explained
Most keyboards don't wire every key individually — instead, keys sit at the intersections of a row-and-column matrix, which lets a keyboard with dozens of keys use far fewer physical wires and controller pins. The tradeoff is that certain combinations of simultaneously pressed keys can create an unintended electrical path through that matrix, causing a "phantom" keypress (ghosting) or a real key silently failing to register (jamming/blocking).
Diode isolation
Most gaming mechanical keyboards solve this by placing a small diode at every single switch, which only allows current to flow in one direction through that key's position in the matrix. This electrically isolates each key from its neighbors, which is what allows a diode-per-switch keyboard to reliably report many keys held down at once — the technical basis for a genuine N-Key Rollover (NKRO) claim.
Why cheap membrane keyboards struggle
Budget membrane keyboards typically skip per-key diodes to save cost, relying on a simpler rubber-dome matrix. This makes certain 3+ key combinations prone to ghosting, which is why many office keyboards can fail on common gaming combos like W + A + Shift even though each key works perfectly fine on its own.
# Gaming Combination Stress Test Guide
Use the combo stress test above to check the key combinations that matter most for your genre: WASD movement plus Shift (sprint) and Space (jump) for shooters, or dense multi-key chords for rhythm games. Press and hold every listed key together when you start a combo test — if any key fails to register as held, that combination may be at risk of ghosting on your keyboard.
# Benchmark Reference Table
| Matrix type | Max simultaneous keys | Ghosting risk | Gaming suitability |
|---|---|---|---|
| Basic membrane (no diodes) | ~2-3 reliable | High | Not recommended for gaming |
| 6KRO USB (boot protocol) | 6 non-modifier keys | Low above 6 keys | Fine for most games, some limits in dense combos |
| 10KRO | ~10 keys | Very low | Good for most competitive gaming |
| Full NKRO mechanical (diode per switch) | Effectively unlimited | Minimal | Ideal for competitive/rhythm gaming |
| Optical/Hall-effect | Effectively unlimited | Minimal | Ideal — often adds adjustable actuation too |
This tool reports what your browser actually received from your OS and keyboard during testing — it can reveal real ghosting/blocking, but a "no ghosting detected" result reflects only the combos you tested, not a guarantee for every possible combination your specific keyboard might struggle with.
# Frequently Asked Questions
Ghosting happens because most keyboards wire keys into a grid, or matrix, of rows and columns rather than giving each key its own dedicated wire. When certain combinations of keys are pressed at the same time, the electrical signal can complete an unintended path through the matrix, causing a phantom key to register or a real key to be silently dropped.
Many mechanical keyboards support full NKRO but ship in a 6-key-limited USB Boot Protocol mode for maximum compatibility, such as with BIOS screens. Check your keyboard's manufacturer software or an onboard key combo (often listed in the manual) to switch it into NKRO or N-Key Rollover USB report mode.
Membrane keyboards typically rely on a simple rubber-dome matrix without per-key diodes, making them prone to ghosting and often limited to a handful of reliable simultaneous keys. Most gaming mechanical keyboards add a diode to each switch, electrically isolating each key from the others in the matrix, which is what allows many of them to claim full N-Key Rollover.
No. Browsers deliberately reserve certain operating system and browser-level shortcuts, such as Alt+Tab, Ctrl+Alt+Delete, or closing a tab, so that no webpage can hijack them for security and usability reasons. This tool can capture and display the vast majority of gaming-relevant key combinations, but a small set of reserved system shortcuts will never reach any webpage's JavaScript.