Keyboard Tester
Check every key, measure rollover and ghosting, catch a stuck switch, and read what your keyboard actually sends. In your browser, with no sign-up.
Keys are captured while the test runs, so Tab and Space will not scroll or navigate. Press Escape twice to release your keyboard. F5, F11 and F12 always pass through.
- Held right now
- 0
- Max at once
- 0
- Keys tested
- 0 / 87
- Total presses
- 0
Max at once 0. Keys tested 0 of 87.
Held keys (event.code)
US ANSI tenkeyless layout shown. Keys that are not on the diagram, such as the numpad and media keys, still count and are listed above. Hover a key to see its press count.
Last key event (for keybind debugging)
- event.key
- —
- event.code
- —
- keyCode (legacy)
- —
- location
- —
- repeat
- —
Ghosting vs. NKRO in 30 seconds
Two different faults, two different symptoms. The tester shows both directly.
- 2KROBasic office boards. Any two keys at once are guaranteed, and a third can be dropped.
- 6KROMost USB keyboards. Six regular keys plus the modifiers, which is the USB boot-protocol limit.
- NKROEvery key reports independently, however many you hold. Nothing is ever dropped.
Rollover is how many simultaneous keys your keyboard can report. Basic office boards guarantee 2, most USB boards do 6 keys plus modifiers, and NKRO boards report every key independently.
Ghosting comes from the key matrix. Without a diode per key, three pressed keys forming an L in the wiring grid can look electrically identical to four, so the board either invents a phantom press (a ghost) or, far more commonly, blocks the extra key and your real input is dropped mid-fight. Anti-ghosting marketing usually means selective blocking around WASD. True NKRO means nothing is ever dropped. Blocked keys never light up, and ghosts light up on their own.
What each key event reports
The five fields the readout prints, and which one your game or macro tool wants.
- event.key
- The character produced, after modifiers and keyboard layout. Shift plus 1 is "!" here.
- event.code
- The physical key, layout independent. Always Digit1, whatever the layout prints on the cap.
- keyCode (legacy)
- The old numeric code. Deprecated, but still what many games and macro tools store.
- location
- Which of a duplicated key fired: 0 standard, 1 left, 2 right, 3 numpad.
- repeat
- Whether the operating system auto-repeated a held key rather than you pressing it again.
The diagram covers 87 keys. Anything else your keyboard sends is still captured and named in the list above the readout.
Plain-text readout
The same last event as one block of text, ready to paste into a bug report or a Discord thread.
Press a key to fill this in.
How to test your keyboard
- Every-key check. Press each key once. It lights up while held and stays marked once tested, so any key that never lights up is dead.
- Rollover (NKRO) test. Press and hold as many keys as you can, palms welcome. Held right now is your live count and max at once is your record. Try gaming combos like ShiftWASpaceCtrl.
- Ghosting test. Hold three or four close-together letters, for example QWE, then add R. If a key you are physically holding never lights up, it is being blocked. If a key you are not touching lights up, that is a ghost.
- Stuck-key check. Release everything. The held list should empty instantly. Anything that lingers is flagged after 8 seconds and has a stuck switch or a missed key-up.
- Keybind debugging. The last-event readout shows
event.key,event.code, the legacykeyCodeand the left or right location. Useful when configuring game binds, AutoHotkey or a remapper.
While the test is running, keydown events are intercepted with preventDefault, so nothing scrolls, types or navigates. Escape hatches: press Esc twice quickly to release your keyboard, and F5, F11 and F12 are never blocked. Everything runs locally. No key data ever leaves your browser.
FAQ
What is key rollover (NKRO)?
Rollover is how many keys your keyboard can register at the same time. A 2KRO board guarantees any 2 keys, 6KRO guarantees any 6, and NKRO (n-key rollover) means every key registers independently no matter how many you hold. Gaming keyboards advertise NKRO so combos like Shift+W+A+Space never drop an input.
What is keyboard ghosting?
Keyboards wire keys in a grid (matrix). On cheap boards without per-key diodes, holding three keys that form an L-shape in the matrix can make the electronics see a phantom fourth key you never pressed: a ghost. To avoid sending ghosts, most boards instead block (jam) the extra key, so your real keypress is silently dropped. Anti-ghosting and NKRO designs fix this with diodes.
Why does the count stop around 6 keys?
Many keyboards run in the USB boot-protocol mode, which reports at most 6 regular keys plus modifiers (Shift, Ctrl, Alt, Win) at once. Some boards need a special NKRO mode or a driver toggle to go beyond 6. If you hit exactly 6 plus modifiers, that is the protocol limit, not a broken keyboard.
Why don't Fn or some media keys show up?
The Fn key is handled inside the keyboard's own hardware and never reaches the operating system, so no software can see it. Media keys, macro keys and some laptop specials may be intercepted by the OS or drivers before the browser gets an event. The Windows key registers, but the OS may still open the Start menu when you release it.
How do I find a stuck or broken key?
Press every key once. Any key that never lights up on the diagram is dead. A stuck key shows the opposite symptom: it appears in the held-keys list (or stays lit) even after you let go, or shows up as held the moment the tester starts. Keys held longer than 8 seconds are flagged as possibly stuck.
Does anything I type leave my browser?
No. Every keypress is handled locally by the page. No key data is sent anywhere, nothing is stored between visits, and the tester works offline once the page has loaded.