Keyboard Ghosting Test
Hold keys on the virtual keyboard and see how many the browser registers at once. Try combos such as WASD + Shift + Space, and see which keys never arrive together. Runs in your browser.
The browser cannot see the Win key menu, Cmd+Q, Cmd+Tab, Alt+Tab, Ctrl+Alt+Del, the Fn key, or media keys handled by the OS or keyboard firmware. Caps Lock, Num Lock, Scroll Lock, and Print Screen flash and are not held, because their keyup events are unreliable. On a Mac, keys released while Cmd is held may not send a key-up, so they are cleared when Cmd is released. Everything is released if the window loses focus or this box blurs.
How this keyboard ghosting test works
Ghosting vs. blocking
Most keyboards wire their switches in a grid of rows and columns. Press three keys that form three corners of a rectangle on that grid, and the controller can see current flowing through the fourth corner too. That phantom press is true ghosting. Nearly every modern keyboard prevents it by blocking (also called jamming): it simply ignores the key that would cause the ambiguity. So in practice, "ghosting" today means keys that silently do nothing.
Cheap membrane boards save money by leaving out a diode on each switch, so only a few combos are safe. The maker picks those carefully (WASD often works), while combos like Q+W+E+R+T or Shift+W+A can fail. "Anti-ghosting" on the box often means just that: 19 or 26 hand-picked keys, not true N-key rollover.
6KRO, NKRO and USB modes
The basic USB keyboard report (boot protocol) has room for 6 normal keys plus 8 modifiers, which is why so many boards stop at exactly 6. NKRO keyboards use a different report format. Many need an NKRO toggle (often an Fn combo), and some fall back to 6KRO in the BIOS, through a KVM switch or over Bluetooth. That is why this test counts Ctrl, Shift, Alt, and Win apart from other keys. It still only counts events the browser delivered, and it cannot see the USB report.
Reading your result
Hold keys one by one and watch the counter. If it stops climbing while you keep adding fingers, the browser stopped receiving new keys for that combo. Six non-modifier keys matches a 6-key USB boot report, and ten is more than that report can hold. Neither number is a USB-mode or matrix reading. Try the combos you use, because one combo can arrive while the next one drops keys.
For games, try WASD + Shift + Space first. If a key never lights up on its own, the browser is not receiving it. That can be a dead switch, or a key the OS or the keyboard handles before the page. A key that types twice is a different fault: try the keyboard double click test.
Laptop keyboards
Laptop keyboards are almost always basic matrices with no diodes. Many register W+A+S+D but drop Space or Shift on top, or fail W+D+Shift. Some gaming laptops advertise "anti-ghosting" for only a small cluster of keys. Run the gaming combo here before blaming your reflexes.
Related tools
Check for chattering switches with the keyboard double click test, measure tap speed with the spacebar clicker or the spacebar counter, and test your mouse buttons and scroll wheel with the mouse tester.
Frequently asked questions
What does this test count?
It counts distinct keys the browser delivers while the test box is focused. A key is added on keydown and removed on keyup, using the event code. Auto-repeat does not raise the count once that code is already down. The number is how many keys reached the page, not a USB mode or a switch-matrix reading.
Do Shift, Ctrl, Alt, and the Win or Command keys count?
Yes. They are drawn on the keyboard and included in Held now and Max at once. Max non-modifier leaves them out. When the browser sends Caps Lock, Num Lock, Scroll Lock, or Print Screen, that key flashes and is not kept down, so it does not raise the simultaneous count. Those four cannot be added to a custom combo.
How do I stop capturing keys?
Click outside the box, or press Escape twice within two seconds without another new key between the presses. While the box is focused, Space and Tab stay in the test, so the page does not scroll and focus does not move. Clicking away, blurring the window, or hiding the tab releases every held key and does not record that attempt. The attempt is recorded only when you release the last key while the box is still capturing.
Why can keys stay lit on a Mac after I let go?
macOS often skips keyup for other keys while Command is held, so this page cannot hear the release yet. When Command itself is released, every non-modifier key still shown as held is cleared. Fn, media keys, and shortcuts the OS handles, such as Command+Tab, Alt+Tab, or Ctrl+Alt+Del, never arrive, so they cannot be shown.
What do the red and yellow keys mean?
After a combo attempt, a chosen key that was not in your best overlap is named under Did not register together and drawn with a red border. A key that was down then, but was not part of the combo, is named under Unexpected keys and drawn with a yellow border. The same words are in the result, not only the color. A free test has no red or yellow marks. It lists the peak set, and any keys that arrived only outside that peak.
Does a high count mean the keyboard is NKRO?
No. If more than 6 non-modifier keys reach the browser at once, those events got past a 6-key USB boot report on the way to the page. This page cannot see the keyboard USB mode, diodes, or matrix. Receiving exactly 6 non-modifier keys matches that report, but it does not prove a further key was dropped. When a further key never arrives, the keyboard, the OS, or the browser may be the reason.
What do the combo tests check?
WASD + Shift + Space, Q W E R T, and the 10 home-row keys are presets. Custom combo stores up to 30 keys. Click Edit, then press or click a key to add it, and press or click it again to remove it. Pressing Escape does not add Escape. Clicking the Esc key on the drawing does add it. A pass means every chosen key was down at the same time. Extra keys do not fail the pass. Keys that arrived only outside that peak are listed as never at the peak.