Keyboard key test
Press any key on the keyboard and its key cap lights up at once. Use it to track down a key that has stopped responding, or to check whether a key gets dropped when you hold several at once (the keyboard’s rollover). 104 keys are covered, including the numpad and the editing keys.
- A few combinations are taken by the browser or the system before the page ever sees them — do not read that as a dead key:
Ctrl+W(close tab),Ctrl+T(new tab),Alt+Tab(switch window),Ctrl+Shift+Esc(Task Manager) and theWinkey on the keyboard. - When you press a function key such as
F11orF12, the browser may act on it first (full screen, developer tools). That is normal too.
Key log
The last 12 presses, newest on top.
How to tell a dead key from poor rollover
- Press each key once, one after another. A key that has been pressed takes on the “seen” colour, so after one full pass it is obvious at a glance which keys are still dim — those are the dead ones. You do not have to watch the screen while you press, which is what makes this so good for catching contact problems that come and go.
- Now hold three to six keys at once. If each key lights up on its own but one goes dark when they are pressed together, that is the keyboard’s rollover falling short (ghosting), not a dead key. A membrane keyboard generally recognises only 6 keys at once; on a mechanical keyboard it depends on the switches and the diode design.
- Watch the “Most held at once” figure. You are holding five keys and it shows three: two were eaten by the keyboard. That number is the most direct evidence there is on rollover.
Where this test stops
All a browser can see is the key presses the operating system forwards to it. When the keyboard firmware detects a conflict it simply discards the conflicting key, and the system never knows you pressed it — so when “a key did not light up”, this page can only report that faithfully; it cannot tell you whether the keyboard ate the press or the key itself is broken. The way to tell them apart is step 1 above: press it on its own.
Also, this page cannot measure how a key feels or how far it has to travel. A switch’s actuation point, its tactile bump and how worn it is all need your hands and specialised equipment; all a web page gets is the instant of the press and the instant of the release. What it can measure is timing and whether anything is missed — nothing more.
Common questions
Press that key on its own first. If it does not light up on its own either, the key is broken; if it lights up on its own but not when pressed together, the keyboard’s rollover falls short — what is commonly called ghosting. Membrane keyboards generally recognise only about 6 keys at once, and different combinations behave differently. That is decided by the hardware design, and only a different keyboard fixes it; no system setting is involved.
Because the browser or the system has taken those combinations, and a web page cannot stop it. Ctrl+W closes the tab, Ctrl+T opens a new one, Alt+Tab switches windows, and the Win key — all of them are handled before the browser gets the event. To test those keys, use dedicated keyboard testing software, or test them in the BIOS.
That is normal, not a stuck key. While the window is unfocused the browser stops receiving keyup, so the page has no way to know you have released. This page clears the key state itself when the window loses focus, so what you see is keys going out on their own rather than staying lit. If you did nothing and a key stays lit and never goes out, that really is a stuck key.
Because the system’s auto-repeat is deliberately filtered out. While you hold a key down, the operating system sends the press event over and over, several dozen times a second — that is software simulating repeated presses, not you pressing. This page excludes those events using KeyboardEvent.repeat, so only a real press is counted.
