Keyboard Tester

When a key stops working, the cause is usually dirt, a worn switch or a loose connection, and the sooner you find which key it is, the easier the repair or the warranty claim. When you buy a new keyboard you also want to know whether it can handle several keys at once. This tester lights up every key as you press it, in the browser, with no software to install.

How to use it

Press Start testing, then press each key on your keyboard. A key turns blue while it is held and green once it has registered, so a key that never changes colour has not sent a signal. While testing is on, the page keeps most keys from doing their usual job. Press the same button again to stop testing when you are done, or Reset to clear the greens.

Identifying keys

The tester reads the physical key code rather than the character, so a key is recognised by its place on the keyboard, whether the layout is US, German or French. The diagram is a full-size ANSI layout with 104 keys. Keys that are not on it, for example some media or function keys, are listed under Keys not on the diagram with their code, which tells you the key was received.

A worked example

On a full-size keyboard, press every key; the count under the diagram rises to 104 of 104. Hold Shift, Ctrl and Alt together with the letters A, S and D. The Held now figure shows the number of keys down at that moment and Held keys names them, for example ShiftLeft + ControlLeft + AltLeft + KeyA + KeyS + KeyD. Most at once keeps the highest number reached, 6 in this example. A keyboard with full N-key rollover reports every key you press, so with ten fingers down the figure is 10.

Rollover and ghosting

Keyboards scan a matrix of switches. Cheap designs cannot tell some combinations apart and either ignore a key or invent one, which is ghosting. USB keyboards using the basic boot protocol report at most six keys plus modifiers at once. Gaming keyboards that advertise N-key rollover report all of them. To test, hold a group of keys that you often use together, for example W, A, Space and Shift, and see whether all of them show.

What the page cannot do

A web page cannot capture the keys that the browser or operating system keeps for itself, such as Ctrl+W, Alt+F4, Ctrl+Alt+Delete and the system or logo key. Some function keys act on the hardware or a driver, and never reach the browser. So a key that is missing here does not prove a fault; try it in another program.

Edge cases

Laptops lack the number pad, and compact keyboards leave out other keys, so a full 104 of 104 is only possible on a full-size board. Any key the diagram does not know is listed by its code under Keys not on the diagram. Holding a key down triggers the system’s key repeat, which does not affect the test.

Limits

It does not measure latency, actuation force or switch quality. It cannot test the keyboard backlight. Nothing you type is stored or sent anywhere.

Related tools

• Mouse Test checks buttons, wheel and double-click faults on a mouse.
• Gamepad Tester tests controller buttons, sticks and vibration.
• Touch Screen Test checks multi-touch on a phone or tablet.
• Dead Pixel Test checks the screen for faulty pixels.