What is keyboard ghosting?

Strictly, it's a phantom key. On a board without a diode on each switch, holding three keys in the wrong combination makes a fourth one look pressed. Most boards prevent that by blocking, which means ignoring the key that could be a ghost. Gamers call both ghosting, since what you actually notice is a key that stops working while you hold others.

How do I know if my keyboard has N-key rollover?

Hold the game chord, then add keys until a new tile won't light. If the Besides modifiers count reads 7 or more, your board isn't limited to 6-key rollover. A true N-key board keeps lighting every key you add. If you get exactly 6 and your keyboard's software has a rollover setting, check it.

Is 6-key rollover enough for gaming?

Usually. W, A, S, D, Shift and Space are 5 regular keys and one modifier, so the whole chord fits inside 6-key rollover. The limit only bites when you hold more than 6 regular keys at once, like movement plus several ability keys.

Why does A go dark when I press D?

That's Snap Tap or SOCD, a setting that keeps only the last pressed of two opposite keys. Pressing D makes the keyboard send a release for A on purpose, so you change direction without lifting your finger. The test reads it as SOCD active, not ghosting. Run the Snap Tap test

Why doesn't the test call ghosting on its own?

A browser can't tell a blocked key from a dead switch or a key you didn't quite press. All three send nothing. So the test waits until the missing key works by itself, then asks whether you were holding it.

Does the result change on Linux?

No, the count tops out at the same number. Past its limit, a 6-key board sends an error report instead of keys. Linux ignores that report, so the keys already down stay lit and only the newest one stays dark.

Keyboard Ghosting Test

Hold W, A, S, D, Shift and Space together and see if your keyboard drops a key. An online check for ghosting and 6-key or N-key rollover.

Vadim Cheban November 3, 2026

Hold W, A, S, D, Shift and Space at once, the keys you sprint, strafe and jump with in a shooter. If one of them never lights, your keyboard dropped it. The test counts how many keys your board passes at the same moment and tells a Snap Tap setting apart from a real fault.

Why a key drops out

Most keyboards wire their switches in a grid of rows and columns, and the controller scans that grid to see which keys are closed. Without a diode on each switch, certain combinations of three held keys let current flow backward and make a fourth key look pressed. That phantom key is ghosting in the strict sense. To stop that, most controllers ignore any key that could be a ghost. That’s blocking. Neighbors in the grid aren’t always neighbors on the keyboard, so the combinations that fail can look random.

What you notice in a game is the blocked key. You hold Shift and W, add Space, and the jump never happens. Many boards sold as anti-ghosting have a grid laid out so the usual gaming keys don’t collide, and can still block other combinations. A board with a diode on every switch and N-key rollover passes any combination.

6 keys or every key

Over USB, a keyboard can use the basic report every PC understands at startup. It has room for 6 keys plus the modifiers (Shift, Ctrl, Alt and Win or Cmd). That’s 6-key rollover. Press a seventh and, per the USB spec, the keyboard sends an error code instead of the key list. The seventh never registers. An N-key rollover board sends a larger report, and every key you hold comes through.

The game chord fits inside that limit, since Shift is a modifier. A 6-key board should pass it, so a fail on the chord points to blocking in the grid, not the USB report. To check past the limit, keep the chord down and add letters. If the Besides modifiers count reads 7 or more, you don’t have a 6-key board.

Snap Tap and SOCD look like ghosting

Hold A and press D with Snap Tap, SOCD or last-input priority on, and the keyboard lets go of A for you. The two never count as held together. The setting is doing its job. You can see it in the timing. A’s release and D’s press land within 1 ms of each other. Let go of D and A comes back just as fast. See that swap 2 times on A and D, or on W and S, and the verdict reads SOCD active. The chord then needs one key fewer for that pair. Want to time your own counter-strafes on A and D or W and S? Run the Snap Tap test.

When a key never shows up

A key that stays dark could be blocked, past your board’s limit, or not pressed all the way. So the test won’t call ghosting by itself. Let go of everything and tap the dark key on its own. Once it lights, you know the switch is fine, and the verdict asks whether you were holding it with the others. Report it and the verdict turns to Ghosting, naming the keys that were down and the one that dropped. To check every key on the board one at a time, use the keyboard tester.

How to use

Click the page. Click once anywhere on the page so it gets your key presses. Typing in the search box or any other text field doesn't count.
Hold the game chord. Press and hold W, A, S, D, Shift and Space together. Each tile stays green for as long as the browser sees that key held.
Add more keys. Keep the chord down and press extra letters with your free fingers. Stop when the Besides modifiers count passes 6 or a new tile stays dark.
Check a dark key on its own. If a tile stayed dark, let go of everything and press that key by itself. Once it lights, report it if you were holding it with the rest.

Why test this

A dropped key in a game feels like lag, and it's hard to prove. You hold sprint and strafe, hit jump, and nothing happens. The cause can be the keyboard's wiring, its rollover limit, a Snap Tap setting, or your own timing. Testing the exact chord shooters lean on settles it in a few seconds. Check a new board while you can still send it back and a used one before you pay. Run it again the day one game starts eating your jumps. If the chord comes through here but still fails in one game, look at that game's bindings. If it fails here, the limit is in the keyboard, and no setting inside the game will fix it. Hold ability keys on top of movement? Then you also want 7 or more in the Besides modifiers count.

What the results mean

The big number is the most keys held at the same moment, modifiers included. Besides modifiers leaves out Shift, Ctrl, Alt and Win or Cmd, so it's the one to compare with the 6-key USB limit. Game chord shows the most of W, A, S, D, Shift and Space you had down together. No ghosting means all 6 came through at once. SOCD active means your board lets only one of A and D, or of W and S, through at a time. Then 5 of 6 is a full pass, or 4 of 6 if both pairs swap. A partial count lists the keys still to hold. Press a missing key alone and the verdict asks if you were holding it. Say yes, and it switches to Ghosting and lists which keys were down and which one dropped. The SOCD readout names each pair where the pattern showed up.

Example result of the Keyboard Ghosting Test: 9 keys held at once, 8 besides modifiers, and all 6 game keys lit for a No ghosting verdict.

FAQ

What is keyboard ghosting?: Strictly, it's a phantom key. On a board without a diode on each switch, holding three keys in the wrong combination makes a fourth one look pressed. Most boards prevent that by blocking, which means ignoring the key that could be a ghost. Gamers call both ghosting, since what you actually notice is a key that stops working while you hold others.
How do I know if my keyboard has N-key rollover?: Hold the game chord, then add keys until a new tile won't light. If the Besides modifiers count reads 7 or more, your board isn't limited to 6-key rollover. A true N-key board keeps lighting every key you add. If you get exactly 6 and your keyboard's software has a rollover setting, check it.
Is 6-key rollover enough for gaming?: Usually. W, A, S, D, Shift and Space are 5 regular keys and one modifier, so the whole chord fits inside 6-key rollover. The limit only bites when you hold more than 6 regular keys at once, like movement plus several ability keys.
Why does A go dark when I press D?: That's Snap Tap or SOCD, a setting that keeps only the last pressed of two opposite keys. Pressing D makes the keyboard send a release for A on purpose, so you change direction without lifting your finger. The test reads it as SOCD active, not ghosting. Run the Snap Tap test
Why doesn't the test call ghosting on its own?: A browser can't tell a blocked key from a dead switch or a key you didn't quite press. All three send nothing. So the test waits until the missing key works by itself, then asks whether you were holding it.
Does the result change on Linux?: No, the count tops out at the same number. Past its limit, a 6-key board sends an error report instead of keys. Linux ignores that report, so the keys already down stay lit and only the newest one stays dark.

How we measure

Each press and release that reaches the browser carries an event code naming the physical key, and that code is what the test counts. It skips the repeats a held key fires. When a release goes missing, the test handles it like the keyboard tester. Every event carries Shift, Ctrl, Alt and Win or Cmd flags, so a modifier whose release got lost still clears. On a Mac, letting go of Cmd clears the keys pressed under it. Leaving the page clears every held key.

Keys at once is the most keys held down at the same moment. Besides modifiers is the same count without Shift, Ctrl, Alt and Win or Cmd, because the basic USB keyboard report holds 6 keys plus the modifiers. A reading above 6 there means your board reports more than that.

The game chord is W, A, S, D, Shift and Space, 6 keys, and either Shift counts. It passes once all 6 are down at the same moment, at any point in the run.

Snap Tap and SOCD leave a timing pattern no hand makes. One key of A and D, or of W and S, lets go and the other goes down within 1 ms. Releasing the second key brings the first back inside that same 1 ms. After 2 swaps on one pair, the test marks it as SOCD, and the full chord is one key short for each marked pair. Hold both keys of a pair down together for more than 1 ms, and the test stops marking that pair as SOCD until you reset. A keyboard with SOCD never lets both stay down.

A missing chord key is a fault only after you confirm it. The test asks you about it once that key has lit on its own and no chord key is down, because a key you never pressed looks the same as one the board dropped.

What a browser cannot see

Only what reaches the browser counts. A blocked key, a key past the board's rollover limit and a dead switch all look alike: no press.

Timing comes from when each event reaches the page. In our runs, Firefox gave those times in whole milliseconds, which still fits the 1 ms window. We confirmed the SOCD pattern on one keyboard with last-input priority. Other SOCD modes are unchecked, and a software tool that does the same thing looks identical, so the verdict names the behavior, not the brand. A run with no SOCD pattern means none showed up this time, not that your keyboard lacks the feature.

Two keyboards plugged in at once count as one, since key events don't say which device sent them. Fn and system shortcuts like Alt+Tab or Cmd+Tab never reach the page. Inside an embedded frame, click the test before it gets keys.

Sources

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