Keyboard Ghosting & N-Key Rollover Test
Hold multiple keys simultaneously — detects ghosting, blocking, and max rollover
Rollover Types
Results are estimates based on browser event timing. Actual hardware values may vary due to OS scheduling and browser overhead.
The Keyboard Ghosting & N-Key Rollover Test detects how many keys your keyboard can register simultaneously. Hold multiple keys at once and see exactly which ones are blocked or ghosted. Essential for FPS and fighting game players who need reliable multi-key input.
What Is Keyboard Ghosting?
Keyboard ghosting happens when pressing multiple keys simultaneously causes a key to either be missed (blocking) or a phantom key to appear (ghosting). This occurs because most keyboards use a matrix circuit where rows and columns share wires — certain combinations create ambiguous electrical states that the controller cannot distinguish.
In a 2D key matrix, pressing three keys at the corners of a rectangle causes the fourth corner to appear pressed even though it isn't. This "ghost" keypress can trigger unintended actions in games.
Rollover Types Explained
- 2KRO: Only 2 simultaneous keys reliably registered. Old membrane keyboards, some budget USB keyboards. Causes problems in virtually all fast-paced games.
- 6KRO: Up to 6 keys simultaneously. The USB HID standard limit for keyboard boot protocol. Sufficient for most gaming scenarios — most actions require fewer than 6 simultaneous keys.
- NKRO (N-Key Rollover): Every key has an individual circuit, allowing all keys to be pressed simultaneously without any blocking or ghosting. Found in quality gaming keyboards. Typically requires full-speed USB or PS/2.
Which Games Require NKRO?
Games where simultaneous keypresses are critical:
- FPS games (CS2, Valorant): W+A/D+Shift+Space+Ctrl simultaneously during movement — 5 keys
- Fighting games (Street Fighter, Tekken): Complex directional inputs combined with attack buttons
- Rhythm games (osu!, Clone Hero): Up to 8–10 simultaneous keypresses in high-difficulty charts
- RTS games: Hotkeys combined with modifier keys for complex commands
Test Tip: For FPS games specifically, hold W+A+D+Shift+Space+Ctrl and check if all 6 register. These are the most common movement + action keys pressed simultaneously in games like CS2. If any fail, your keyboard has a problematic rollover limitation for competitive play.
Frequently Asked Questions — Keyboard Ghosting & N-Key Rollover Test
Keyboard ghosting occurs when you press multiple keys simultaneously and one or more keypresses go unregistered — or a phantom "ghost" key appears that was never pressed. This happens because standard keyboard matrix circuits cannot always distinguish all combinations of simultaneous keys. In fast-paced games like FPS shooters where you might hold WASD + Shift + Space simultaneously, ghosting can cause you to stop moving unexpectedly or miss critical inputs during combat.
6KRO (6-Key Rollover) means the keyboard can accurately register up to 6 simultaneous keypresses — the USB HID standard limit. Most gaming keyboards offer 6KRO which is sufficient for the vast majority of games. NKRO (N-Key Rollover) means every single key has its own electrical pathway and can be pressed simultaneously with all other keys without any ghosting or blocking. NKRO typically requires a PS/2 connection or a gaming keyboard with special USB NKRO firmware.
No. While marketing often implies it, many mechanical keyboards only offer 6KRO over USB. True NKRO is found on premium gaming keyboards like the Ducky One, Leopold FC900R, and Corsair K70. Some keyboards offer NKRO only when connected via PS/2 adapter. Use this ghosting test to verify actual rollover performance of your specific keyboard rather than relying on marketing claims.
Press and hold keys that you would normally use simultaneously in games — for example, hold W+A+Space+Shift+Ctrl (sprint-jump-strafe). Watch the visual keyboard layout and the "Keys Held" counter. If the counter stops incrementing or shows fewer keys than you are physically holding, your keyboard is ghosting or blocking those keys. The "Rollover Type" badge will update to show the maximum simultaneous keys your keyboard supports.
The most common ghosting zones are around the WASD cluster when combined with Shift, Ctrl, Space, and nearby letter keys. Specifically: W+A+D with Shift or Ctrl is a notorious ghosting combination on budget keyboards. The number row with modifier keys also frequently ghosts. Diagonal movement (W+A or W+D) combined with any third key is where most gaming keyboards first show their rollover limits.
No, and this is a common marketing confusion. "Anti-ghosting" typically means the manufacturer has optimized the key matrix to prevent phantom (ghost) keystrokes from appearing — but does not guarantee full simultaneous key registration. N-Key Rollover (NKRO) is the stronger specification that guarantees every key registers independently. A keyboard can be "anti-ghosting" (no phantom keys) while still blocking certain simultaneous combinations.
Yes — browsers receive keydown and keyup events for every key the keyboard reports to the OS. If your keyboard supports NKRO and the OS is correctly receiving all simultaneous key inputs, the browser will receive and display all of them. The only limitation is that some browser keyboard shortcuts (like Ctrl+W which closes a tab) may interfere with testing those specific key combinations. For those keys, test in a dedicated keyboard testing application.