Frame Rate Test

Keyboard Ghosting Test

Check your keyboard for ghosting and N-key rollover (NKRO) in seconds.

Click the keyboard to focus it, then press and hold several keys at once. Keys that register light up green. Watch the max count to see your keyboard's rollover — and spot any keys that fail to register (blocking) or any you didn't press lighting up (ghosting).

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No keys held — press a combination and hold it.
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Combos to try: gaming W + A + S + D + Shift + Space, or a same-row stress test Q + W + E + R + T + Y. If a held key won't light up, your keyboard is blocking that combo to avoid ghosting.

How to read this: the browser only sees the keys your OS reports, so this shows your effective rollover in the browser. Many keyboards register only 6 keys at once over USB (6KRO) by default; true N-key rollover lets every key register independently. If keys fail to appear when you hold a combo, that is blocking (good — it prevents ghosting); a key lighting up that you never pressed would be ghosting. Note that some combinations are reserved by your operating system — for example ⌘ + Spaceopens Spotlight on macOS — and are intercepted before the browser sees them, so they can't be tested here. Stick to letter and number combos for the truest rollover reading.

This free online keyboard ghosting test detects ghosting and checks your keyboard's N-key rollover. Press and hold several keys at once and the on-screen keyboard lights up every key that registers, tracking the maximum number of simultaneous keys — so you can see exactly how many keys your keyboard handles together and which combinations it blocks.

Want to check every key one at a time? Find dead or stuck keys with the full Keyboard Tester.

Keyboard Ghosting Test Guide

What Is Keyboard Ghosting?

Keyboard ghosting happens when you press a combination of keys and the keyboard either drops one of them or registers a key you never pressed. It comes from how a keyboard's key matrix is wired: on a basic keyboard, certain three-key combinations share electrical paths the controller cannot tell apart. Ghosting is most noticeable in games, where you might hold movement keys plus a modifier and find an action simply does not fire.

Ghosting, Blocking & Rollover

  • • Ghosting: a phantom key registers that you did not press — the worst case, and rare on modern keyboards.
  • • Blocking (anti-ghosting): instead of ghosting, the keyboard ignores the extra key. Safer, but a key press is still missed.
  • • Rollover (NKRO / 6KRO): how many keys can be held at once with all of them registering. Higher is better.

How to Use the Test

  1. 1. Click the on-screen keyboard so it captures your key presses.
  2. 2. Press and hold a combination — try W + A + S + D + Shift + Space.
  3. 3. Every key that registers lights up green; the count shows how many are held at once.
  4. 4. Add more keys and watch the Max Simultaneous figure — that is your rollover.
  5. 5. If a held key never lights up, your keyboard is blocking that combination. Press Reset to start over.

Reading Your Rollover

Max simultaneous keysWhat it means
2–5Limited rollover — common on basic membrane keyboards; blocks easily.
6 (6KRO)The standard USB boot-protocol limit, fine for most typing and casual play.
7–9Beyond the USB limit — a strong anti-ghosting keyboard.
10+ (NKRO)Effectively full N-key rollover — every key registers independently.

Browser & Hardware Notes

  • • The browser only sees the keys your operating system reports, so this is your effective rollover, not a hardware datasheet figure.
  • • Many keyboards register 6 keys at once over USB by default and enable full NKRO only in a special mode or via their software.
  • • Modifier keys (Shift, Ctrl, Alt) are handled separately and usually do not count toward the matrix limit.
  • • Use the Windows / Mac toggle above the keyboard to match your hardware — the Mac view shows the ⌘ Command, ⌥ Option, and ⌃ Control keys.
  • • Some combos are reserved by your OS (for example ⌘ + Space opens Spotlight on macOS) and are intercepted before the browser sees them — test rollover with letter and number keys instead.
  • • If a key stays highlighted after you let go, click Reset — a release event can be missed when many keys are down.

Frequently Asked Questions

Keyboard ghosting is when pressing several keys at once causes a key you did not press to register (a "ghost" key), or causes one of the keys you did press to be dropped. It happens on keyboards whose wiring matrix cannot tell certain simultaneous key combinations apart. This test shows which keys register when you hold a combination, so you can spot ghosting and blocking.
N-key rollover means every key on the keyboard is read independently, so any number of keys can be pressed at the same time and all of them register. Keyboards with limited rollover only guarantee a few simultaneous keys — commonly 6 over USB (6-key rollover, or 6KRO). NKRO keyboards are preferred for gaming and fast typing because no key press is ever missed.
Standard keyboards using the USB boot protocol register about 6 keys at once (plus modifiers) — that is 6KRO. Many gaming keyboards support full N-key rollover, where 10, 20, or more keys register simultaneously. To test yours, hold down as many keys as you can and watch the "Max Simultaneous" count climb.
That is blocking (anti-ghosting). Rather than produce a false ghost key, the keyboard simply refuses to register an additional key in a combination it cannot resolve. Blocking is the safe behaviour — it is better to miss a key than to type a phantom one — but it can be frustrating in games. A keyboard with higher rollover blocks far less often.
It measures your effective rollover in the browser, which is what the operating system reports. Some keyboards default to 6KRO over USB and only enable full NKRO in a special mode or via their software, so your true hardware capability may be higher than the browser sees. Older PS/2 keyboards can also behave differently. Use this as a practical, real-world rollover check rather than a hardware datasheet.
On a keyboard with a basic membrane matrix, ghosting and low rollover are hardware limitations that cannot be fixed in software. The solution is a keyboard with anti-ghosting or full N-key rollover. Some gaming keyboards also let you switch on NKRO mode in their companion software, which raises how many keys register at once.

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