Largest chord, in press order: none yet
Ghosting is a key appearing to activate when you did not press it, usually because the keyboard's internal wiring matrix cannot tell that combination of physically held keys apart from a different one that includes it. Blocking is the opposite: a key you are pressing simply never registers. Watch the diagram while holding several keys at once. A key lighting up that you are not touching is ghosting. A key that stays dark no matter how hard you press it is blocking.
Your operating system and browser swallow some combinations before this page ever sees them, such as Windows+L, Alt+Tab, and Ctrl+Alt+Delete. Those never register here, even on a full NKRO keyboard. Many keyboards also fall back to the USB boot protocol, the same legacy mode used by PC BIOS and boot loaders, which can only report up to six regular keys held at once: if the count above always stops at 6, that may be the keyboard reporting in that mode rather than a hard hardware limit.
Details
No key events recorded yet. Start the test and press some keys.
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What it does
Tests how many keys your keyboard can register at once, known as N-key rollover, and helps you spot ghosting and blocking while it happens. Hold down as many keys as you can and watch the count of simultaneously held keys climb, along with a live verdict: 2KRO or blocked, limited, 6KRO, or full NKRO.
How to use it
Click into the panel and hold down keys, ideally in combinations you would actually use, like a movement cluster plus a modifier plus a letter. The diagram lights up each key as it is detected, the counter tracks the largest chord seen so far, and the verdict updates live. Reset and try a different combination to map out where your keyboard's limit sits.
Why this one
Most rollover testers are Flash relics or ad-choked pages that only show a single static grid. This one runs entirely in your browser, updates the verdict live as you press, and never sends a single keystroke anywhere: your inputs never leave your device.
FAQ
- Why does the test often stop registering new keys at 6?
- Many keyboards fall back to the USB HID boot protocol, a legacy compatibility mode (also used by PC BIOS and boot loaders) that can only report up to 6 regular keys held at once plus modifiers. A keyboard advertised as NKRO usually needs a different USB report mode, sometimes toggled by a driver or a key combo, to go past this.
- What is the difference between ghosting and blocking?
- Blocking is a key you are pressing simply failing to register, which is safe: you just do not get that keystroke. Ghosting is a key lighting up that you never touched, caused by the keyboard's internal wiring matrix being unable to distinguish your combination from a different one that includes it. Cheaper keyboards without diode protection on every key are the most prone to ghosting.
- Why do some keys never register at all, like Windows+L?
- Your operating system and browser intercept certain combinations before any web page can see them, for security or system-level shortcuts: Windows+L locks the screen, Ctrl+Alt+Delete opens the OS security screen, and Alt+Tab switches windows. Those never reach this test, or any web page, regardless of your keyboard's rollover capability.