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Key Rollover & Ghosting Test
Hold down several keys at the same time and watch the counter below track exactly how many your keyboard reports at once. This is the practical way to measure rollover (how many simultaneous key presses your keyboard can handle) and to spot ghosting (when the keyboard silently drops or misreports a key because too many are held in the wrong combination).
currently held down tested (pressed at least once) not tested yet
What rollover and ghosting actually mean
Most keyboards wire their keys as a grid of rows and columns rather than giving each key its own dedicated wire, which keeps the electronics cheap and the cable thin. The tradeoff: press the right combination of three or more keys in that grid at once, and the controller can lose track of exactly which ones are down. This effect is called ghosting, and a keyboard's rollover is the maximum number of keys it can reliably report as held at the same time, regardless of which ones.
You will see two common ratings mentioned by keyboard manufacturers: 6KRO (six-key rollover, a common limit for standard USB keyboards, tied to how the USB HID boot protocol reports key presses) and NKRO (n-key rollover, meaning effectively unlimited simultaneous keys, common on higher-end mechanical and gaming keyboards that use a different reporting protocol).
How to test your keyboard's rollover here
Use the on-screen keyboard below exactly like the main keyboard test: it lights up every key you press. The difference here is what to focus on.
- Hold down a single key first to confirm it registers normally (it should turn solid, then settle into the tested highlight when released).
- Add a second key from a different row and column (for example W and O, not two keys that sit right next to each other) and confirm both stay lit while held.
- Keep adding keys, spreading them across different rows and columns of the keyboard rather than one straight line, and watch the "max held at once" counter climb.
- Note the point where an additional key press stops registering (does not light up, or the counter stops increasing) even though you are still physically holding it down. That number is a practical, real-world measurement of your keyboard's rollover.
- Try the same test again with keys clustered close together in the same row or column: ghosting typically shows up sooner in that pattern than when keys are spread out, because it depends on the physical row/column wiring, not just the total count.
Why rollover matters, and when it doesn't
For most everyday typing, occasional ghosting on an obscure key combination is never actually noticed: normal typing rarely holds more than two or three keys down at the exact same instant. Rollover becomes genuinely important in two situations.
- Gaming, especially games that use several movement/action keys held simultaneously (a common example is holding forward, strafe, and jump, or a directional key plus multiple ability keys at once). A low rollover here can silently drop an input at the worst possible moment.
- Fast typing and touch-typing, where your fingers briefly overlap on the next key before fully releasing the previous one. A keyboard with poor rollover on the home-row keys can occasionally miss a character during fast bursts, which shows up as an inexplicable typo that was not actually a typing mistake.
Interpreting your result
| Max held at once (measured here) | What it suggests |
|---|---|
| 6 or fewer, regardless of key layout | Typical of a basic USB keyboard using the standard 6KRO boot protocol. Fine for everyday use, may occasionally drop a key during fast gaming. |
| More than 6, but drops in specific row/column patterns | Partial rollover, common on many membrane and laptop keyboards. The specific dropped combinations depend on the internal wiring and will be consistent if you repeat the test. |
| Every combination you try keeps registering | Likely full NKRO, common on higher-end mechanical keyboards. You are very unlikely to ever notice a dropped key from rollover alone. |
If you want to check individual keys rather than combinations, use the main keyboard test tool, or read the stuck key troubleshooting guide if a specific key is not responding at all, even alone.
This test is not a substitute for checking individual keys
A low rollover count is a design characteristic of your keyboard's electronics, not a fault, and cleaning or repairing anything will not change it. If a single key fails to light up here even when pressed completely on its own, that is a different problem: see the dedicated guide to fixing a stuck or unresponsive key instead.
6KRO vs NKRO: what the specification sheet actually promises
If you are comparing keyboards before buying, the rollover figure on a spec sheet describes a ceiling under specific, often best-case, conditions, not a guarantee for every possible combination of keys. A keyboard advertised as NKRO over USB usually achieves it through a vendor-specific driver or a non-boot HID report mode; plugged into a BIOS screen or a device that only reads the basic boot protocol, the same keyboard can fall back to 6KRO behavior. If full rollover matters to you for a specific use case (competitive gaming being the most common one), it is worth testing the exact combination of keys you actually use, in the exact software environment you use it in, rather than trusting the number on the box alone. This page gives you a fast, no-install way to do exactly that.
No key data from this test is ever sent anywhere either, see the full privacy policy for details.