Ghosting is when a third key refuses to register, or a key you never touched appears, because of how the keyboard matrix is wired. The guided mode asks you to hold a series of three-key sets, from WASD gaming combos to same-column triples that break cheap boards, and records which key went missing. Switch to hold-anything mode to test your own combinations and click any key that will not light up. Try the keyboard test next if you want another angle on how your keyboard behaves.
Hold all three; the set passes when all three light up
Hold together
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0 / 18 combinations
Hold the highlighted keys together.
Held right now (0)
none
Blocked keys (times)
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Combination log
Run this keyboard ghosting test to find out whether your keyboard drops keys when you hold several down at once, whether you are gaming or typing. It is a free online anti-ghosting check: press multiple keys, watch what registers on screen, and you will know whether your board is a true NKRO keyboard or a ghosting risk. There is no download and no signup, and the answer appears instantly in your browser.
Use the keyboard tester above this guide as your ghosting and multi-key checker. Click the page once so it has focus, then hold your chosen combination and compare the lit keys with the keys under your fingers. The tester draws a key history and shows each key as held down or released on the on-screen layout. Run the mac keyboard test to see your result in seconds, right in your browser.
Work from easy to hard so you can see exactly where your keyboard gives up:
Without browser focus the tester sees nothing, so click inside the page first. Extensions and operating system shortcuts, such as Windows key combinations, can swallow key events and other input before the page gets them. Rule those out before you blame a hardware fault.
Keyboard ghosting is a hardware limitation: when several keys are pressed together, the keyboard fails to report all of them correctly. A key you held may never arrive, or a key you never touched may show up. It hurts gamers, fast typists and anyone chaining hotkeys, because a sprint key that dies mid-dash or a chord that will not fire in your editor costs real time. Ghosting only shows up under simultaneous key presses, so a keyboard can seem fine for years of everyday typing before you notice. Programming and accessibility setups that rely on chords feel it too. Run the typing speed test to see your result in seconds, right in your browser.
A ghost key is a signal for a key you did not press. The reverse case is a dropped key: a key you did press is swallowed. Both come from the same electrical ambiguity, but they look different in a test. Phantom inputs light up unprompted, while a blocked key stays dark.
Do not confuse this problem with monitor ghosting, the trailing blur behind moving objects caused by slow pixel response. It is the same word for completely different hardware, and a display check is the right tool for that one.
Most keyboards do not wire every switch to its own line. They share lines in a grid, and firmware scans that grid hundreds of times per second to see which crossings are closed. Run the mechanical keyboard switch tester to see your result in seconds, right in your browser.
In a switch matrix, each key sits where one row and one column cross. A single press closes one crossing, which gives the firmware a unique address. Hold three keys that form an L shape across two rows and two columns, and current can flow through a fourth, unpressed crossing. That phantom intersection is the ghost. Which combinations fail depends on the exact row and column layout the maker chose, so one zone can pass while another fails.
Gaming boards add a diode to each switch. A diode stops current from flowing backwards through the circuit, so every press produces an unambiguous signal no matter how many other keys are down. Anti-ghosting technology of this kind, applied to every key, is what earns the label N-key rollover. Many a mechanical keyboard aimed at gamers has it, while cheap membrane boards often skip the extra parts to save cost, and the switches themselves make no difference.
Key rollover is the number of keys a keyboard can report at the same moment. The number before "KRO" is that limit, and N-key rollover means there is no limit at all: with NKRO, every key is detected independently however many are held.
| Rollover type | Keys reported at once | Where you find it |
|---|---|---|
| 2KRO | 2 regular keys | Basic office keyboards |
| 6KRO | 6 keys plus modifiers | Most USB keyboards |
| Full NKRO | Every key | Gaming boards built for it |
A 2-key rollover board is fine for plain typing. 6-key rollover covers most games, and NKRO removes the ceiling. An NKRO test, a keyboard rollover test or an n-key rollover test on a true NKRO keyboard shows every key lit, however many you press.
A PS/2 connection can report every key at once, but the standard USB keyboard protocol reports only six regular keys plus modifier keys. Many keyboards sold as NKRO reach that limit only in a special mode, and over USB they fall back to 6KRO. A wireless keyboard connected over Bluetooth is usually capped even lower. This tester shows what your keyboard does in your current setup, so run it with the cable you actually use.
Dana, who plays a shooter on a wired 87-key board, wants to know why the reload key sometimes dies during a sprint-and-strafe. The decision on the table: keep the board or return it within the 30-day window. I would start with the claim on the box, "NKRO", and check it rather than trust it.
The hold is the one Dana actually uses: W, A, Q, E, R and Space with Left Shift, then F added for a heal. That is six regular keys plus one modifier first, then seven regular keys plus the modifier. The board is plugged directly into a USB port on the computer, and the page has focus.
With six regular keys and Shift held, all 7 of 7 light up. Adding F, the on-screen layout still shows only 7 lit, and F stays dark. What stands out is the number: a standard USB keyboard report carries six key codes plus one modifier byte, so a board capped at 6KRO shows exactly this cut-off. It is a 6KRO ceiling, not a broken switch.
| Regular keys held | Shift held | Keys lit | Missing |
|---|---|---|---|
| 4 | Yes | 5 | 0 |
| 6 | Yes | 7 | 0 |
| 7 | Yes | 7 | 1 |
| 8 | Yes | 7 | 2 |
The rerun matters most. Changing one input, the number of regular keys, moves the missing count from 0 to 1 at exactly the seventh key, and that break point is the finding. Dana also swaps the order and presses F first. Now a different key drops out, which proves the limit is about how many keys, not which key. The number to watch is the first count where lit keys stop growing.
One caveat: this does not show a ghost key. A clean 6-key cap is a rollover limit, and a true matrix fault would drop keys at three or four, in specific corners. Dana's next move is concrete: open the keyboard software, switch the board to its NKRO mode, and rerun the same seven-key hold. If F lights, the box was right and the board stays. If it stays dark, the return goes ahead.
Ghosting is zone-specific, so test the combinations you really use instead of random keys.
Try Ctrl + Shift + a letter, the multi-modifier shortcuts used in code editors, and A + S + D + F followed by G with the first four still held. Avoid system-reserved sets such as Ctrl + Alt + Delete, which the operating system intercepts before any page sees them.
Treat every anti ghosting keyboard test result as evidence, not a verdict. If every held key lights up together, that combination reached your browser. If something is off, the next two steps tell you what kind of fault you are looking at.
A missing key means the full combination was not reported, which points to a clash in the matrix. An extra key means a stray key appeared, which points to a ghost intersection. A pattern that repeats in one corner of the keyboard narrows the cause to that part of the matrix.
Before you decide the keyboard is faulty, retest with the page focused and without system-reserved sets. If keys register but arrive late, that is a latency issue, so use a polling rate or latency check rather than this one.
Software cannot repair a missing part, but a few steps remove the false alarms, and the right diagnostics tell a ghosting problem from a different typing fault.
Look for a spec sheet that states full NKRO over USB, not only through a legacy port. Among gaming keyboards, hot-swappable mechanical models usually list their rollover plainly. Test any new keyboard with this page inside the return window, and keep the combos you use most in mind when you do.
Ghosting happens when you press several keys at once and the keyboard fails to report all of them, or reports a key you never pressed. It comes from the way many keyboards share wiring in a switch matrix.
NKRO means every key is detected on its own, however many are held at once. Boards with 6KRO report six regular keys plus modifier keys, and 2KRO boards report only two.
Hold the key and watch it light up on the on-screen layout, then release it. A key that stays dark after you press it may be unresponsive, blocked or not reaching the browser.
Usually the page does not have focus. Click anywhere on the page first, then try again. Browser extensions and operating system shortcuts can also swallow key events, so disable them for the test.
No. Monitor ghosting is a trailing blur behind moving objects caused by slow pixel response. Keyboard ghosting is about keystrokes that never arrive or arrive when you did not press them.
Test the ones you really use: W, A, S and D together, W plus Shift plus Space, Q, W, E and R, and multi-modifier shortcuts such as Ctrl, Shift and a letter. Ghosting is zone-specific, so a combination can pass in one area and fail in another.
Yes. PS/2 can report every key at once, while the standard USB keyboard protocol reports six regular keys plus modifiers. Many boards sold as NKRO only reach that over PS/2 or in a special mode.