Keyboard Ghosting & Rollover Test.
Ghosting is when a keyboard drops one of the keys you're holding because too many are pressed at once. This test measures how many keys your board can register together — your rollover — so you know whether it will keep up when you type fast or game.
Click here to start testing simultaneous inputs (NKRO)
Tip: Press modifier keys (Shift, Ctrl, Alt) along with standard letter keys for maximum count.
Keys Currently Held
Test Log — keys registered per burst
Hold a group of keys, then release — each attempt is logged here.
Rollover Stats
Rollover Levels Explained
Check these before you test
- Connect directlyHubs and KVM switches can force a board down to 6-key rollover; use a direct USB port.
- Enable NKRO if you have itMany boards ship in 6KRO/BIOS mode — flip the NKRO switch or Fn toggle to test the full matrix.
- Hold keys you actually useTest real clusters like W A S D + Space, not random keys, to see rollover that matters to you.
How to run the rollover test
- 1
Focus the test box
Click the box above so it starts listening for simultaneous key presses.
- 2
Hold a cluster
Press and hold a group you really use — for gaming try W A S D + Space, or mash several letters at once.
- 3
Read the count and log
Watch how many register together; release, and the log records the peak of each burst so you can spot dropped keys.
Ghosting vs. rollover — what's the difference?
Inside most keyboards the keys sit on a grid of intersecting wires called a matrix. The controller scans that grid to find which switches are closed. When you hold several keys that share the same rows and columns, the controller can get an ambiguous reading — so it either drops a key (ghosting, a keypress you made that never registers) or blocks the extra input entirely (jamming, where new presses simply do nothing until you let go).
Rollover is the fix. It describes how many keys a keyboard can report at the same time without losing any. "6-key rollover" (6KRO) guarantees at least six simultaneous keys plus modifiers — the limit of the standard USB keyboard protocol. "N-key rollover" (NKRO) lifts that cap so every key is reported independently, which needs a keyboard that either uses a diode per switch or switches its USB into a full NKRO mode.
For everyday typing even a 2KRO board is usually fine, because you rarely hold more than a couple of keys at once. It matters most for gaming — think holding forward, strafe, and jump while pressing a fourth action — and for fast typists whose keystrokes overlap. If the count above climbs past six, or keeps rising as fast as you can add fingers, your keyboard has proper anti-ghosting.
When to use this test
Before a competitive match
Confirm your movement and action keys all register together so you never lose an input mid-fight.
Buying a gaming keyboard
Verify an "NKRO" claim actually holds up past six keys before you rely on it.
A combo won't fire in-game
Find out whether the board is ghosting the third or fourth key rather than the game ignoring it.
Fast typing drops letters
Overlapping keystrokes can exceed a cheap board's rollover — measure where yours tops out.
Anti-ghosting glossary
- Ghosting
- When pressing several keys at once causes one or more to silently fail to register.
- Jamming / blocking
- When a keyboard refuses extra presses entirely until you release, instead of dropping one.
- Rollover (6KRO / NKRO)
- How many keys register at once — 6KRO guarantees six plus modifiers; NKRO reports every key independently.
- Matrix
- The grid of row and column wires a controller scans to detect presses; its layout is what causes ghosting.
Anti-Ghosting FAQ
How many keys should register at once?
It depends on what the keyboard advertises. Six standard keys plus your modifiers (Shift, Ctrl, Alt, Cmd/Win) is the USB HID baseline and is enough for the vast majority of people. Gaming and mechanical keyboards labelled "NKRO" should let you keep adding keys well past six with none dropping. If your board caps out at two or three non-modifier keys, that's basic 2KRO and you may notice dropped inputs in games.
My count stops around 6 even though the board says NKRO. Why?
A hard stop at six non-modifier keys almost always means the keyboard is running in 6KRO / "USB boot" mode rather than full NKRO. Many boards ship that way for BIOS compatibility and expose an NKRO toggle — look for an Fn shortcut (often Fn + N) or a setting in the keyboard's software. USB hubs and KVM switches can also force a board back down to 6KRO, so try a direct port.
Does the specific combination of keys matter?
Yes — on non-NKRO keyboards, ghosting depends on the matrix wiring, so some three-key combinations jam while others don't. That's why the log here records the actual keys in each burst: if you press four keys but only three appear, note which one dropped and try a different cluster. A true NKRO board registers every combination equally, no matter how the keys are grouped.
Is this the same as testing for a stuck or chattering key?
No. This page measures how many different keys work together. For a single key that sticks, repeats, or double-fires, use the main Keyboard Tester to see if it lights up on its own, or the Event Logger to catch duplicate events from one press.
Do I actually need N-key rollover (NKRO)?
For everyday typing, no — you rarely hold more than two or three keys at once, so even a basic 6KRO board never drops an input. NKRO matters if you game, especially when you hold movement keys and press an action at the same time, or if you type fast enough that keystrokes overlap. If you press four or more keys together and see them all counted above, your board already has enough rollover for what you're doing.