Press and hold multiple keys at the same time to see which ones register. Ghosted keys appear in red, active keys in orange. Tests your keyboard's N-key rollover limit in real time.
Keyboard Test
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👻
Keyboard Ghosting Test
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⚡ Low Latency🔒 Privacy
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Ghost Log
No combos detected yet. Press multiple keys.
Testing:
Key Rollover Guide
N-KRO
♾️ Full Rollover
No ghosting
6-KRO
⚡ Gaming Grade
Most games OK
4-KRO
🎮 Good
Most combos OK
3-KRO
📖 Average
Light gaming
2-KRO
🐢 Casual
Typing only
1-KRO
🔴 Poor
Ghosts badly
👻
What is Keyboard Ghosting?
Ghosting occurs when a keyboard fails to register a key you pressed because too many other keys are held simultaneously. It's caused by how cheaper keyboards share electrical circuits across multiple keys. If you're chasing input delay too, pair this with our latency tester to get the full picture of your keyboard's responsiveness.
♾️
N-Key Rollover (NKRO)
NKRO means every single key has its own dedicated line to the controller. You can press every key at once with no missed inputs. Most gaming keyboards advertise 6KRO or full NKRO over USB. A solid rollover score also tends to translate into better results on our typing test, since dropped keys during fast bursts can cost you accuracy.
🔲
Keyboard Matrix & Ghosting
Standard keyboards use a row-column grid. When three keys share two rows and two columns simultaneously, the controller sees a phantom fourth key or misses one entirely — the classic ghost triangle. Curious how this affects real typing speed? Run our wpm test alongside this one to see if ghosting is holding your numbers back.
🎮
Why It Matters for Gaming
In fast-paced games, pressing W+A+Shift+Space simultaneously is common. If your keyboard only supports 3KRO, one of those inputs will be dropped, causing your character to stop or fail to jump at a critical moment. Worth checking your input delay with the latency tester, and if you type as much as you game, our typing test and wpm test round out the full keyboard checkup.
Frequently Asked Questions
Ghosting is when your keyboard fails to register a key you pressed because too many other keys are held at the same time. It is caused by the shared-matrix design used in most standard keyboards to reduce manufacturing cost. Gaming keyboards use diodes on each key to prevent this.
N-key rollover (NKRO) means the keyboard can register every key pressed simultaneously, no matter how many. Each key has its own dedicated electrical path to the USB controller. Most standard keyboards support 2–4 key rollover. Gaming keyboards commonly support 6KRO or full NKRO.
The test listens to the browser's keydown and keyup events. When you hold multiple keys, it counts how many are registered simultaneously. If a key you are physically holding does not appear highlighted, your keyboard is ghosting it. The test cannot detect phantom keys because they would appear as unexpected registrations.
Yes — 6KRO keyboards register up to 6 standard keys at once, plus modifier keys like Shift, Ctrl, and Alt which are typically handled on separate lines and do not count toward the rollover limit. This is sufficient for the vast majority of gaming scenarios.
The USB HID keyboard protocol has a 6-key limit per report packet for standard key codes. Modifier keys are transmitted in a separate byte, so they bypass this limit. To achieve full NKRO over USB, manufacturers use a custom driver or the USB Boot Protocol workaround. PS/2 connections have no such limit and naturally support NKRO.
Yes. The keyboard display reflects the live state of currently held keys. When you release them, the highlights clear. The maximum simultaneous count and the ghost log are preserved so you can review your results without holding keys down.
⚙️ Settings
Show F-Key Row
Display the function key row on the keyboard visual
Show Arrow Keys
Display the directional arrow cluster
Show Number Row
Display the top digit row (1–0) on the keyboard
Show Bottom Row
Display Ctrl / Win / Alt / Space row
Show Status Bar
Live "Keys Held" status bar inside the zone
Show Rollover Bar
Progress bar showing current rollover level
Theme Accent
Colour used for buttons and highlights
Active Key Colour
Highlight colour for currently held keys
Key Release Fade
Show green tint on recently released keys
Key Press Scale
Animate key shrink on press
Key Glow Effect
Box shadow glow on held keys
Key Label Style
How key names are displayed on each key
Keyboard Layout
Visual layout of the keyboard display
Auto-log Combos
Automatically record every multi-key combination to the ghost log
Min Keys to Log
Minimum simultaneous keys before a combo is recorded
Ghost Detection Mode
How the test identifies blocked keys
Ignore Modifier Keys
Don't count Shift / Ctrl / Alt toward rollover score
Track All Key Types
Include function, media, and navigation keys in tracking
Log History Limit
Max number of combos stored in the ghost log
Zone Background
Background style of the main keyboard zone
Show Grid Dots
Dot grid pattern overlaid on the zone background
High Contrast Mode
Increase border and text contrast across the page
Large Font Size
Increase label and result text size
Reduce Motion
Disable key press animations and transitions
Compact Layout
Reduce padding in the keyboard zone for smaller screens
Key Press Sound
Play a click sound when a key is registered
Ghost Alert Sound
Play a warning tone when a ghosted key is detected
New PB Sound
Chime when a new max simultaneous record is set
Sound Volume
Volume level for all in-tool sound effects
Sound Style
Tone character for key press feedback
Show Rollover Guide
Key rollover tier reference chart below the test
Show Info Cards
Ghosting / NKRO info cards below the test
Show Side Stats
Rollover Result panel in the side column
Show Ghost Log
Recent key combos log in the side column
Highlight Active Tier
Highlight the current rollover tier in the guide
Result Detail Level
How much detail to show in the side stats card
High Contrast Mode
Stronger borders and increased text contrast
Large Font Size
Increase all text sizes for easier reading
Reduce Motion
Disable animations, fades, and transitions
Focus Outline
Show visible focus ring on interactive elements
Screen Reader Mode
Add ARIA live regions for key press announcements
Clear Ghost Log
Remove all logged key combinations from this session
Reset Session Stats
Reset rollover count, unique keys, and combo totals
Export Ghost Log
Download logged key combos as a CSV file
Reset All Settings
Restore all settings to defaults and clear stored data
❓ Help & Guide
🎯 How to Use This Tool
1
Press and hold down multiple keys at once — no clicks needed, the tool captures key events globally.
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Keys that register appear highlighted in orange. The live counter shows how many are held.
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Add more keys gradually. The Max Simultaneous counter locks in your keyboard's rollover score.
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If adding a key causes others to disappear from the display, ghosting / blocking has occurred.
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Use Mode pills (WASD, Gaming, Arrows) to focus on the key zones most relevant to your use case.
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Check the Rollover Result panel in the side column for your full keyboard assessment.
⌨️ Key Capture Notes
The tool captures all key events globally — no need to click the keyboard first.
Modifier keys (Shift, Ctrl, Alt, Win) use separate HID lines and rarely ghost.
Ctrl+W, Ctrl+T and similar combos are intercepted by the browser and won't appear.
F11 toggles browser fullscreen — the press is captured after the browser acts on it.
💡 For the most accurate test, use a wired connection. Wireless keyboards can drop simultaneous inputs due to transmission timing.
🔢 Reading the Numbers
Active — Keys currently held down and registered by the OS
Ghosted — Keys the tool detected as blocked this session
Max Sim. — Your keyboard's peak simultaneous key count — the rollover score
📊 Key Rollover Explained
Key rollover (KRO) is the number of keys a keyboard can register simultaneously without any being lost. It is determined by the keyboard's internal electronics — specifically whether keys share matrix lines or have dedicated paths.
📋 Rollover Tiers
Type
Max Keys
Typical Use
Common On
1-KRO
1
Basic text entry
Very old keyboards
2-KRO
2
Standard typing
Office membrane
3-KRO
3
Casual gaming
Budget keyboards
6-KRO
6
Competitive gaming
Gaming keyboards
NKRO
All
Pro / RTS / typing
Mechanical / PS/2
🔌 USB vs PS/2 Rollover
The standard USB HID keyboard protocol transmits up to 6 key codes per report packet. Modifier keys (Shift, Ctrl, Alt) travel in a separate byte and don't consume this limit. PS/2 has no such restriction, making it inherently NKRO.
To achieve NKRO over USB, manufacturers use a custom HID descriptor that splits key codes across multiple reports. This usually requires enabling a special mode on the keyboard (e.g. holding Fn+N on boot).
💡 If your mechanical keyboard claims NKRO but you only get 6 keys, check the manufacturer's guide — you may need to manually enable NKRO mode.
⚡ Modifier Key Exception
Shift, Ctrl, Alt, and Win keys each occupy a dedicated bit in the HID modifier byte, completely separate from the 6-key standard key array. This is why you can always press Shift+Ctrl+Alt+any 6 keys without ghosting — the modifiers are free.
👻 What Is Ghosting?
Ghosting happens when a key you physically pressed is not registered by your computer. It occurs because multiple keys share the same electrical row and column lines in the keyboard matrix. When their combinations create ambiguous current paths, the controller drops inputs rather than guess wrong.
🔴 Ghosting vs Blocking
These are two distinct failure modes often confused with each other:
Ghosting — A key you pressed doesn't register. The input is silently dropped.
Blocking / Jamming — All keys in a conflicting matrix group stop registering when a third key is added. You lose multiple previously-working inputs.
Phantom keys — A key registers that you never pressed, caused by ambiguous matrix current paths.
💡 This tool detects blocking (previously registered keys disappearing). True phantom injection is rare and would appear as a key highlighting without a physical press.
🧲 Anti-Ghosting Diodes
Adding a diode to each key switch ensures current can only flow in one direction through the matrix. This eliminates phantom current paths, allowing the controller to correctly identify every pressed key regardless of combinations. All genuine mechanical keyboards use per-key diodes. Most membrane keyboards do not — they rely on careful key grouping instead.
🗺 Problem Key Zones
On standard membrane keyboards without full anti-ghosting, the most commonly ghosted combinations involve keys in the same matrix block:
Q + W + E — Top row cluster
A + S + D — Home row cluster (critical for WASD gaming)
Shift + multiple letters — Shift shares rows with letter keys on budget boards
🔲 How a Keyboard Matrix Works
A keyboard matrix is a grid of wires — rows and columns — that the controller scans rapidly. Each key sits at the intersection of one row and one column. When you press a key, it connects that row to that column, and the controller identifies the intersection as "pressed."
This design is efficient: a 6×14 grid handles 84 keys using only 20 wires. But it creates ambiguity when multiple keys share rows and columns simultaneously.
⚠️ The Ghost Triangle Problem
Imagine keys A, B, and C where A and B share row 1, B and C share column 2. When you press all three, current from row 1 flows through B's column to the row of C — making the controller think D (the fourth intersection of those row/column combinations) is also pressed. This is the classic ghost triangle that causes phantom keys.
Without diodes, the keyboard must either register the phantom (bad) or drop some inputs entirely (blocking) to avoid confusion.
✅ Diode Solution
Adding a diode at each key switch creates a one-way valve: current can flow from column to row, but never backward from row to column. This breaks the ghost triangle — the phantom current path has no return route. The controller correctly reads exactly which keys are physically pressed.
🔁 Controller Scan Rate
The matrix controller doesn't read all keys at once — it activates each row in sequence (usually at 1,000 Hz / 1ms intervals). All keys pressed during a scan cycle are bundled into a HID report and sent to the host. A faster scan rate means lower input latency and more accurate simultaneous registrations.
MOBA (League, Dota 2) — 4–6 KRO for ability + movement combos
RTS (StarCraft, AoE) — NKRO strongly preferred; hotkey-heavy play needs all keys
MMO / RPG (WoW, FFXIV) — 4-KRO usually sufficient for ability rotations
Fighting Games — 6-KRO minimum for simultaneous directional + attack inputs
Platformers / Indie — 3-KRO generally OK
Casual / Office — 2-KRO is fully sufficient
📐 Testing Your Gaming Combos
Switch to Gaming mode using the pills above the keyboard, then hold down your exact in-game key combination. Every key that lights up orange is registered. Any key your character "misses" in-game corresponds to a key that disappeared from the display — that's your ghosting zone.
💡 The WASD mode highlights only movement and action keys, making it easy to spot ghosting without distraction from the full keyboard.
🖥 Keyboard Types & Rollover
Type
Typical KRO
Anti-Ghost?
Standard membrane
2–3 KRO
Partial
Budget gaming membrane
3–6 KRO
Zone-based
Mechanical (gaming)
6 KRO or NKRO
Full (diodes)
Optical mechanical
NKRO
Full (optical)
PS/2 connection
NKRO
Full (protocol)
Laptop built-in
2–3 KRO
Minimal
⚡ Switch Types & Input Quality
Mechanical linear — Smooth, fast actuation, excellent for gaming. Examples: Cherry MX Red, Speed Silver.
Mechanical tactile — Tactile bump at actuation point, good for gaming + typing. Examples: Cherry MX Brown, Topre.
Optical — Light beam detection, virtually zero debounce, ideal for NKRO. Examples: Razer OmniPoint, Wooting Lekker.
Membrane dome — Rubber dome over membrane sheet. No per-key diodes in most cases. Lowest rollover.
🔌 Connection & Polling Rate
Wired USB — Most reliable, standard 1,000 Hz polling, 6-KRO by default, NKRO possible with driver.
Wireless 2.4 GHz — Near-wired latency (~1ms), but simultaneous key registration can drop under heavy RF interference. May ghost under load even if the keyboard hardware supports NKRO.
Bluetooth — Higher latency (8–20ms), not recommended for competitive gaming. Rollover usually capped at 6 KRO.
PS/2 — No USB protocol limits. True NKRO with zero USB latency overhead. Rare on modern motherboards but still available via adapter.
🛠 Enabling NKRO on Gaming Keyboards
Most gaming keyboards default to 6-KRO USB mode for maximum compatibility.
NKRO mode is typically activated by holding Fn + a key (check your keyboard manual — commonly Fn+N, Fn+F9, or Fn+Scroll Lock).
Some keyboards switch automatically when a supported driver is installed.
In BIOS / pre-boot, keyboards often revert to 6-KRO for compatibility.
📊 Reading Your Results
Max Keys Simultaneous — The highest number of keys registered at the same time. This is your effective KRO score.
Rollover Type — Classification based on max simultaneous: 1-KRO through N-KRO.
Anti-Ghosting — Confirmed if you reached 4+ keys without any dropping. "Limited" means blocking was detected before 4 keys.
Gaming Ready — Yes for 6KRO+, Partial for 4-5 KRO, No for under 4.
Ghosted Keys Found — Count of keys that registered then disappeared when additional keys were pressed.
Unique Keys Pressed — Total distinct key codes received this session — useful for checking coverage.
Peak Combo Size — Same as Max Simultaneous; retained for clarity in the results card.
Combos Tested — Number of multi-key combinations you've held down and released this session.
Connection Type — Inferred from your rollover score: PS/2 or NKRO USB if 10+, standard USB if 6, legacy if under 4.
Verdict — Overall badge combining KRO tier and gaming readiness.
📈 Rollover Bar
The progress bar in the keyboard zone fills as you increase your simultaneous key count. It maxes out visually at 10 keys (N-KRO threshold). The label updates in real time to show your current rollover level.
📋 Ghost Log
Every time you release a multi-key combination, it is added to the Ghost Log in the side panel. Each entry shows the keys in the combo, how many were held, and whether all keys registered (OK) or some were dropped (Ghost). Use this log to map exactly which specific combinations cause ghosting on your keyboard.
🏆 Getting the Best Score
Use a wired connection — wireless can drop inputs at high simultaneous counts even on good hardware.
Close other tabs — browser-intercepted shortcuts (Ctrl+W, Ctrl+T) can't be captured and will reduce your combo count mid-press.
Press keys slowly and deliberately — mashing quickly may cause timing gaps that undercount simultaneous registrations.
Start with WASD + Shift + Space — the most common gaming ghosting zone on budget keyboards.
Try pressing 10+ keys to confirm NKRO. Use all fingers across the home row.
🔬 Diagnosing Problem Combos
Hold a combo until all keys are lit, then add one key at a time. The key that causes another to disappear is the ghosting trigger.
Check the Ghost Log after each release — entries show exactly which combos caused issues.
Test the same combo multiple times. Consistent drops indicate hardware limits; occasional drops may be software or timing.
Try the same combo with Caps Lock on/off — some keyboards ghost differently depending on the Caps Lock state.
🛒 Upgrade Advice
If this test reveals ghosting in your typical gaming combos, here's what to look for when upgrading:
Look for "full anti-ghosting" or "NKRO" in the keyboard spec sheet.
Mechanical keyboards with per-key diodes always have full anti-ghosting.
Budget gaming keyboards may advertise "26-key anti-ghosting" — this means specific zones, not the full board.
Optical switches (e.g. Wooting, Apex Pro) offer NKRO with the lowest possible debounce delay.
🔧 Troubleshooting
Keys not lighting up at all? — Check browser focus. Try clicking anywhere on the page first, then press keys.
Fewer keys than expected? — Your keyboard's rollover limit has been reached. The OS drops extra key codes before they reach the browser.
Keys disappearing randomly? — Likely blocking. Note which key triggers the disappearance — that's your ghosting combination.
Score resets on refresh? — Expected. Session stats are not persisted. Use the Export CSV option in Settings → Data to save your results.
📌 Frequently Asked Questions
Is this test accurate? — Yes, within browser limits. The tool reads raw keydown/keyup events, which reflect what the OS delivers. The OS itself receives data directly from the USB HID driver.
Why are some keys always blocked? — The browser intercepts system shortcuts (Ctrl+W, Alt+F4, Win key). These are consumed before reaching the page.
Why does the test show fewer keys than I pressed? — Your keyboard's rollover limit has been reached. Additional key codes are dropped at the hardware or driver level before the browser ever receives them.
My keyboard says NKRO but I only see 6 keys — why? — Most keyboards ship in 6-KRO USB compatibility mode. Check the manual for an NKRO toggle (often Fn+N or Fn+Scroll Lock).
Do modifier keys count toward rollover? — Usually not. Shift, Ctrl, Alt, Win use dedicated bits in the HID modifier byte, separate from the standard 6-key array.
Can this detect phantom keys? — Phantom keys would appear as unexpected key highlights with no physical press. This tool displays all keydown events received, so a phantom would be visible — but uncommon in modern keyboards.
Does the layout affect results? — No. The physical scan matrix is the same regardless of whether you use QWERTY, AZERTY, or Dvorak layout. Ghosting is determined by key position (row/column), not the character label.
My results vary between tests — is that normal? — Small variation can occur due to browser timing. For consistent results, press keys slowly and hold them fully before adding more.