Keyboard test: find dead keys and ghosting
Press every key on your keyboard and watch it highlight instantly. This test shows the raw key code of your last press and counts how many keys you're holding at once, which is the easiest way to catch dead keys, stuck keys, and rollover limits.
Keyboard test
Click into this panel, then press keys. Tested keys turn cyan; keys pressed right now are highlighted solid.
Last key event
no key pressed yet
Keys held right now
0
Max simultaneous (rollover)
0
Keys tested this session (0)
Press any key to start.
Quick guide: how to use the Keyboard Test
Takes under a minute- 1Click once inside the test area so it has keyboard focus.
- 2Press every key, including modifiers and the number pad.
- 3Each key should light up on release and stay marked as tested.
- 4A key that never lights up is dead, remapped, or blocked by the OS.
Overview
A keyboard looks simple from the outside, but under the keycaps it's a grid of switches wired into rows and columns. When you press a key, the controller chip scans that grid dozens of times a second and reports which intersection closed a circuit. Most keyboard complaints, whether it's a key that does nothing, a key that repeats on its own, or a combination of keys that behaves strangely, trace back to something going wrong in that scanning process.
This test gives you a fast, visual way to check the whole keyboard without opening a text editor and squinting at which letters appear. Click into the on-screen keyboard panel above, then work your way across every row, including modifier keys like Shift, Ctrl, and Alt on both sides. Every key you press lights up in cyan and stays lit for the rest of the session, so at a glance you can see which keys you've verified and which you haven't touched yet.
Below the layout, the page also shows you the raw event data from your last keypress: the physical key code, the character it produced, and the legacy numeric keyCode some older software still checks. That detail matters more than it sounds, because it lets you separate two very different problems: a key that truly isn't working, versus a key that's working fine but mapped to the wrong character because of a language or layout setting.
How to read your results
Keys that never light up
If you press a key and it stays grey while everything around it turns cyan, that key isn't sending a signal to your operating system at all. This is the classic sign of a dead key. On mechanical and membrane keyboards it's usually mechanical: dust, a hair, or a small amount of spilled liquid under the keycap is preventing the switch from making contact. On laptops the same thing happens, but the fix is trickier because the switch sits directly on the motherboard's flex cable.
The 'last key event' panel
Every time you press a key, this panel updates with three values. code identifies the physical key position (for example KeyQ is always the key in the Q position, even on a French AZERTY keyboard where it produces the letter A). key is the actual character your system currently maps that position to. keyCode is an older numeric identifier that some legacy web forms and games still rely on. If code updates correctly but key looks wrong, the keyboard hardware is fine and you have a layout mismatch in your OS settings, not a broken key.
Keys held right now and max rollover
The "keys held right now" counter tracks exactly how many keys your browser currently believes are pressed down at once. Hold down three or four keys in a cluster, like W, A, S, and D, and watch the counter. If it stops climbing before you've actually lifted a finger, one of those keys isn't being recognized while the others are held, which points to a rollover limitation in that specific key combination rather than a single dead key.
"Max simultaneous" remembers the highest number this counter ever reached during your session, which is useful for gamers checking whether a keyboard can handle common combinations like strafing plus jumping plus shooting all at once.
Troubleshooting
If a key or group of keys consistently fails this test, work through these steps roughly in order, from least to most invasive:
- Try the same key in a different application to rule out a browser-specific issue, though this is rare since key events are standardized.
- Restart your computer. A surprising number of "dead key" reports are actually a stuck driver state that clears on reboot.
- Unplug and reconnect a USB keyboard, or re-pair a Bluetooth one, to rule out a flaky connection.
- Remove the keycap carefully (most keycaps on mechanical keyboards pull straight up with light, even pressure) and blow out any dust or debris with compressed air.
- If you recently spilled liquid, power the device off immediately, disconnect the battery if it's a laptop, and let it fully dry for 48 hours before testing again.
- Check your OS keyboard layout settings if the physical key registers (code updates) but produces the wrong character.
- If several adjacent keys fail together on a laptop, suspect a torn ribbon cable, which usually needs professional repair or a keyboard replacement.
Why rollover and ghosting matter
Most people never notice rollover limits during typing, because typing rarely requires holding more than two keys at once. It becomes obvious in two situations: fast touch typing where your fingers briefly overlap keystrokes, and gaming, where movement and action keys are frequently held together for seconds at a time.
Cheaper keyboards wire their switches in a simple matrix that can only reliably detect a handful of simultaneous presses in certain combinations. Press a third key in the wrong spot on the grid and either the keyboard drops one of your inputs (an anti-ghosting failure) or, worse, it reports a key you never touched at all (true ghosting). Keyboards marketed as supporting "NKRO" (n-key rollover) or built with per-key diode wiring don't have this limitation and can register every key held down regardless of combination.
Use this test's rollover counter to check a keyboard before you buy it, or before a big project where reliable multi-key shortcuts matter, such as music production software or games with complex control schemes.
Laptop-specific tips
Laptop keyboards fail differently from desktop ones because the whole assembly is thinner and more exposed to crumbs, dust, and spills that fall between keys. A few laptop-specific notes:
- Scissor-switch keys (the flat, low-profile type used in most modern laptops) are harder to remove and reseat than mechanical keycaps, so try compressed air first before attempting removal.
- External keyboard shortcuts for brightness, volume, and media controls are usually intercepted by firmware before they reach the browser, so it's normal for them not to register here.
- If your laptop has a numeric keypad overlay activated by a function key, the digits it produces are reported using whatever code that mode currently assigns, which can look unfamiliar in the raw event data.
- Water damage often doesn't show up immediately. If you spilled something recently and keys pass this test today but start failing over the next week, that delayed corrosion is a known pattern.
Frequently asked questions
How do I test if my keyboard is working?
Open this page and press every key on your keyboard one at a time. Each key you press turns cyan on the on-screen layout, so at the end you can scan for any key that never lit up, which usually means it isn't registering.
What is a dead key on a keyboard?
A dead key is a key that produces no signal when pressed, often due to debris under the keycap, a worn switch, or a loose connection. On a laptop this is frequently caused by liquid spills or years of dust buildup.
What does 'key rollover' mean?
Rollover, sometimes called n-key rollover (NKRO), describes how many keys a keyboard can register accurately at the same time. Most cheap keyboards support only 2 to 6 key rollover, while gaming keyboards often support full NKRO.
What is keyboard ghosting?
Ghosting happens when pressing three or more keys at once causes a phantom key to register that you never pressed, or causes one of the pressed keys to be silently dropped. It's a limitation of the keyboard's internal wiring matrix, not software.
Why does the test show 'code' and 'key' separately?
'code' is the physical key location on the keyboard and never changes with layout, while 'key' is the character your layout and language settings produce. Comparing them helps you tell a hardware problem from a layout or language setting problem.
Can this test detect a stuck key?
Yes indirectly. If a key still shows as 'held' in the pressed count after you've released it and moved on, that's a strong sign it's physically stuck or the switch isn't springing back.
Does this work with external keyboards?
Yes. Any keyboard connected over USB, PS/2, or Bluetooth and recognized by your operating system will send standard key events that this page can read, regardless of brand.
Why do some keys like Fn or brightness not register?
Function keys tied to hardware features (brightness, volume, airplane mode) are often intercepted by the keyboard's own firmware or the OS before they ever reach the browser as normal key events, so they won't show up here.
Is my keystroke data sent anywhere?
No. Every key event is processed locally in your browser's JavaScript and only exists in memory on this page. Nothing is transmitted, logged, or stored on a server.
My laptop's numeric keypad overlay doesn't show separately, why?
Some laptops share physical keys between letters and a numpad overlay (activated with a Fn or NumLock combo). The browser reports whichever code the firmware currently maps that key to, so it will still register, just under one code.
What should I do if a key fails this test?
Try cleaning around the keycap with compressed air first. If it's a laptop key, check whether the manufacturer sells individual keycap and switch replacement kits. If several adjacent keys fail together, the ribbon cable underneath may need replacing by a technician.