How to Check for Keyboard Ghosting and Key Rollover Online

If you have ever been sprinting diagonally in a game, tried to reload, and had nothing happen, you have met rollover limits. The keyboard was not ignoring you out of spite — it had run out of keys it could report at once.

The terms around this get used loosely, including by manufacturers, so it is worth separating them before testing anything.

Ghosting versus blocking

Ghosting, properly defined, is when a key you did not press gets reported. Press Q, W and E together on a badly wired membrane keyboard and R might appear out of nowhere. The keys sit on a grid of rows and columns, and three corners of a rectangle being pressed can make the controller believe the fourth corner is pressed too.

Blocking is the opposite and far more common: a key you did press is not reported. The controller detects the ambiguity and, rather than inventing a phantom keypress, drops the input entirely.

Nearly everything people call ghosting today is actually blocking. Genuine phantom keypresses are rare on any keyboard made in the last decade, because manufacturers add diodes specifically to prevent them. Dropped inputs, though, remain extremely common on cheap and laptop keyboards.

What rollover means

Rollover is the number of simultaneous keys a keyboard can report correctly.

• 2KRO — two keys plus modifiers. Typical of very cheap membrane keyboards and many laptops. Fine for typing, frustrating for games.
• 6KRO — six keys plus modifiers, which is the maximum the standard USB keyboard protocol reports in one packet. Most decent keyboards do this, and it is genuinely enough for almost everyone.
• NKRO — n-key rollover, meaning every key independently. Achieved by the keyboard presenting itself to the computer differently, so it is not bound by the six-key packet format.

Modifiers are reported separately from those six slots, which is why Ctrl+Shift+Alt plus six letters works on a 6KRO board. That detail explains a lot of confusing test results.

Testing it in a browser

You do not need software for this. The browser receives keydown and keyup events for every key the keyboard reports, so a web page can show exactly how many are being held at once — which is what our ghosting and NKRO test does.

The method:

1. Open the test and click once on the page so it has keyboard focus.
2. Hold down one key. Then add a second, a third, a fourth — without releasing any.
3. Watch the count. Keep adding keys until one stops registering.
4. The number of keys lit when the next one fails to appear is your real rollover.

Test with letter keys spread across the board, not clustered. Rollover limits come from the wiring matrix, so results vary depending on which keys you choose. If you care about gaming specifically, test the exact combination you use — usually W, A, S, D plus Shift, Space, Ctrl, R and 1 through 4.

Two things that will skew your result. Browsers reserve some combinations for themselves (Ctrl+W will close the tab rather than register), so stick to letters and arrows. And a few keyboards behave differently in the BIOS than in Windows, because they fall back to a basic mode before drivers load — that is normal and not a fault.

Reading your result honestly

If you hit six keys and stop, you have a 6KRO keyboard working exactly as designed. This is not a defect and there is nothing to fix.

If you stop at two or three, you have a low-rollover membrane keyboard. Also not a defect — it is what that hardware costs. If it is affecting your gaming, the only real fix is a different keyboard.

If you get past six and keep going, you have NKRO working. Some keyboards ship with NKRO off by default and need a Fn shortcut or a software setting to enable it, so a 6KRO result on a board advertised as NKRO is worth investigating rather than treating as a lie.

And if a key you did not touch appears on screen — actual ghosting — that is worth pursuing. On a modern keyboard it usually means a fault rather than a design limit: a damaged PCB trace or a failing diode. It is also worth ruling out key chatter, which can look similar at a glance.

Does any of this matter for you?

For typing, no. Touch typists rarely hold more than three keys simultaneously and the human hand is the limit long before the keyboard is.

For most gaming, 6KRO is genuinely sufficient. Moving diagonally while holding Shift to sprint and pressing an ability is four keys with modifiers reported separately — comfortably inside the budget.

Where it genuinely matters: rhythm games, fighting games with complex inputs, and anything where you hold several movement keys while chording abilities. Those cases do exceed six. For everyone else, NKRO is a feature worth having but not worth buying a keyboard for.

The more common real-world problem is not rollover at all — it is a keyboard that drops inputs because of connection problems, or a key that has physically worn out. Rule those out before concluding your rollover is too low.

FAQ