browser hardware tests

Keyboard ghosting test

This key rollover test counts how many keys your browser receives at the same moment.

Hold several down to see the most that arrived together, or pick a combination to see which never did.

Keyboard Not started

Click the board to begin, then hold several keys down together.

This test reads physical keys. A phone's on-screen keyboard reports no key code, so open this page on a computer to run it. The drawing below is a diagram rather than a readout: it scales to fit the width, so on a narrow screen the caps are too small to read, and the list under it names each key as it registers.

Num Lock ? Caps Lock ? Scroll Lock ?
Escape is a key under test. Press it twice to stop, or use the Stop button.

Held now: 0. Most at once: 0.

Hold as many keys as you can at once. The count keeps the most that arrived together.

Nothing has narrowed the layout down yet, so the board is drawn as ANSI 101. Press a key only your keyboard carries and it redraws. Nothing reports the size, so pick yours above. This browser cannot read which character each key types until you press it, so pick your language above or press the keys.

No keys recorded yet. A key you press is named here, so this test reads without the drawing.

Key events

The latest presses, newest first, as the browser reported them. Held for is how long the key was down: it measures your finger, not how fast the key is. Repeat appears when you hold a key long enough, and it is your system's key repeat setting, not the keyboard.

KeyCodeTypedHeld forRepeat

Windows and macOS keep some keys for themselves: the Windows or Command key, Alt+Tab. This browser can borrow most of them for the test, in full screen, and then Escape becomes a key under test like any other. Press Stop to leave, or hold Escape for two seconds, which the browser handles even if this page stops answering.

How can you test for N-key rollover?

Hold keys down together and the keyboard ghosting test counts how many your browser receives at the same moment. It keeps the most that arrived at once and names them. Pick a combination, hold all of its keys, and the test names each key that never arrived while the others were held. The number describes your keyboard, cable and computer together, not the keyboard alone.

What is keyboard ghosting?

Keyboard ghosting names two opposite faults that appear when several keys are held: a key you press never registers, because the keyboard cannot tell it apart from the keys already down, or a key you did not press registers anyway. A keyboard guards against the second by ignoring new keys when the pattern held on its key matrix is ambiguous, and that produces the first.

This test sees both from the same place: the key codes that reach your browser. A missing key shows up as a key that never arrived. An extra key shows up as a key that lit without a finger on it.

What does key rollover mean?

Key rollover is how many keys a keyboard reports at the same time. A board sold as 6-key rollover, written 6KRO, reports six ordinary keys plus the modifiers. N-key rollover, NKRO or full key rollover, means the maker claims each key reports however many are held.

This test counts what reached your browser, which is the whole chain on this computer, not the rating on the box.

How many keys can your keyboard register at once?

As many as the whole chain delivers: this test shows the most your browser received together, in this combination, on this computer. Hold as many as you can and read the count. Try a second combination before concluding anything, because the limit can depend on which keys you chose as much as on how many.

The keyboard's own claim is printed on its box or in its manual: anti-ghosting, a key rollover figure, or NKRO when the maker claims the whole board. A web page cannot read that claim.

How do you check if your keyboard is ghosting?

Hold W, A, S and D, then press the other keys one at a time. A key that stays gray while those four are held never reached your browser in that combination.

Let go of one of the four and press the gray key again. If it now lights, the limit is about how many keys, or which ones, were down together. The wiring, the firmware, the USB report or the operating system can stop a key, and from a web page they all look the same.

Does stopping at six keys mean your keyboard is 6KRO?

It is consistent with it, and it does not prove it. The simplest USB keyboard report carries six ordinary keys plus the modifiers, so a board using it stops at six letters however many you hold. Shift, Ctrl, Alt and the Windows or Command key travel separately and do not use those six places.

Other limits can stop at six too, and the browser has no way to tell them apart. Hold the eight home-row keys and see whether the count stops at the same place.

Why does holding Command on a Mac change the result?

On macOS, while Command is held, browsers do not receive the release of other keys. It was reported against Chrome and Safari in 2011 and against Firefox in 2016. The newest reply found is from 2023, on the Firefox report, and the current status of the three was not re-checked.

So the count pauses while Command is down, and releasing Command clears the keys it left stuck. Leave Command out of the combinations you test on a Mac.

What can this test not tell you?

Your keyboard's rollover rating
The browser sees the minimum of the whole chain: the keyboard's wiring and firmware, the USB report, the operating system and the browser. The count belongs to that chain, on this computer.
Whether a key was blocked or never pressed
Both arrive as nothing. Naming the keys first is the only way to say which of them did not arrive, and that is what the combinations are for.
Which link in the chain stopped a key
The USB report and the keyboard's wiring both produce a missing key event. The browser never sees the report itself.
Combinations with Command on macOS
Browsers on macOS do not receive other keys being let go while Command is held. The count pauses instead of guessing.
Caps Lock on a Mac
macOS reports Caps Lock turning on and turning off, not the key being held, so the test counts it as a tap and never as part of a chord.
Keys held when the window loses focus
Their release goes to whatever window has focus now, so the test clears them rather than count keys nobody is holding.
Latency and polling rate
No browser interface reports how often the keyboard is polled or how long a press takes to reach the page. The count here is which keys arrived together, not how fast.

What does your result mean?

The whole combination arrived together
Your keyboard, cable and computer deliver that combination. Try one with more keys.
A key never arrived with the others
Something stopped it. Hold one fewer key and try again: if it arrives, the limit is the count; if it still does not, it is that combination.
The count stops at six ordinary keys
Consistent with the simplest USB keyboard report, and not proof of it. Modifiers do not count toward those six.
A key you did not press lit up
It reached the browser as a real key event. That is ghosting in its second sense, a key the keyboard reported with no finger on it.

Common questions

Is anti-ghosting the same as N-key rollover?
No. Anti-ghosting means the keyboard blocks a key rather than report a wrong one, which can still leave a combination incomplete. N-key rollover means each key reports however many are held. A keyboard ghosting test in a browser shows the result of either, not which one the keyboard uses.
Can keyboard ghosting be fixed?
This page cannot tell which link stops the key, so it cannot tell you what to change. Find the combination that fails here, then hold the same keys on a computer with another operating system and browser: if it fails there too, the keyboard is the likely cause. Either way, move the action in your game or app to keys that this test shows arriving together.
Is 6-key rollover enough?
It depends on the keys you hold together, and that is what this test checks. Six-key rollover means six ordinary keys plus the modifiers, so W, A, S, D, Space and Shift use five of the six places. A board can still drop a smaller combination, so hold the ones you use and see whether each one arrives.
How do you test a keyboard for ghost typing?
Click the board, take your hands off the keyboard and wait: a key that lights up reached your browser as a real key press, and the Key events list under the board names it. Ghost typing needs no keys held, unlike the ghosting this page counts. The test cannot see what sent the key, so try the same keyboard on another computer before you blame the keyboard.
Does a wireless keyboard give a different result?
It can, because the receiver and its driver are part of the chain the count describes. Test the same combination wired and wireless if the keyboard supports both.
Why do Shift, Ctrl and Alt not seem to count against the limit?
The USB keyboard report gives each modifier its own bit, separate from the places ordinary keys use. A keyboard that stops at six letters can still report Shift and Ctrl on top of them.
Is this keyboard ghosting test safe to use?
It runs in your browser, and the keys you press are never sent one by one. When a run ends, the page sends a summary: how many keys registered out of how many, and, only when most of the board was tested, up to six key codes that did not. The privacy page lists everything that is sent.

This test's engine last changed on . The page says only what the engine can do, and the two change together.