KeyTest

How to use the keyboard tester

There is nothing to set up. With this page open and focused, start pressing keys:

1. Press and hold a key. The matching key on the on-screen keyboard highlights while it is held and returns to normal when you release it. Holding a key down will not spam the animation — repeats are ignored until you let go.
2. Click or scroll your mouse. The mouse diagram on the right highlights the left, right, middle button, or scroll wheel as you use them. On a touchscreen, a tap counts as a left click.
3. Watch the input history. Every key and click is appended to the history box next to the layout selector, so you can confirm exactly what was registered.
4. Reset anytime. The Reset button clears the history and releases any highlight that may have stuck — handy if a key's release was missed because focus changed mid-press.

If a key does nothing on screen, that key (or its switch) may not be registering — a fast, no-install way to diagnose a faulty keyboard.

What the visualizer shows

On-screen keyboard

A full keyboard, including the function row, navigation cluster, and modifiers. Keys are matched to physical positions, so the layout you see stays consistent regardless of your operating system's input language.

Mouse & touch

Left, right, and middle clicks, plus scroll-wheel up and down. Right clicks are captured without opening the browser context menu, and touch input maps to a left click for tablets and phones.

Special & extended keys

A dedicated panel covers a numeric keypad and the USB HID keys that rarely appear on consumer keyboards — function keys F13–F24, media controls, and system keys — so programmable and full-size boards can be tested too.

Live input history

A running, read-only log of bracketed tokens such as [A] [Space] [left]. It is capped in length, never saved, and cleared by Reset.

Keyboard layouts explained

Use the selector to switch the on-screen keyboard between four distinct physical layouts. The selector labels are in English, while the keycaps keep their native glyphs (Ñ, AltGr, ⌘, and so on).

Key codes: event.code vs event.key

Browsers expose two different identifiers for a keypress, and the difference matters when testing hardware:

• event.code identifies the physical key by position (for example KeyA or Digit1). It does not change when you switch your OS input language.
• event.key is the character produced, which depends on the active layout and modifiers (the same physical key can yield a, A, or á).

KeyTest highlights keys by event.code so the visual position stays stable no matter which language your system is set to. That is exactly what you want when checking whether a specific physical switch is working.

Special & extended keys

Most keyboards expose only a subset of the keys defined in the USB HID Usage Tables. KeyTest includes the extras so they can be detected if your hardware sends them:

• Extended function keys F13–F24 — valid HID codes found on some programmable and older full-size keyboards.
• Media & consumer keys — play/pause, stop, next/previous track, mute, and volume.
• System keys — power, sleep, and wake, plus editing keys like Again, Undo, Cut, Copy, and Paste.

Codes above F24 are not part of the standard keyboard HID tables; if your device emits one, KeyTest surfaces it in an "unrecognized/extended" area rather than guessing at a label.

Who uses an on-screen keyboard tester

• Buyers checking a keyboard — verify every key and switch on a new, used, or repaired board before relying on it.
• Streamers & creators — show viewers which keys and clicks are being pressed during tutorials and gameplay.
• Typing practice & education — give learners immediate visual feedback and demonstrate different layouts.
• Accessibility demos — illustrate modifier keys, sticky keys, and input behavior on screen.
• Developers — inspect the exact event.code a key emits while building web apps.

Troubleshooting keyboard problems

A key doesn't light up

First make sure this page has focus (click anywhere on it). If the key still does nothing, the switch may be failing, or the key may be intercepted by the OS before the browser sees it (some media or vendor keys behave this way).

A highlight gets stuck

If you switch windows while holding a key, the browser can miss the release event and the key stays highlighted. Press Reset to clear stuck highlights.

Several keys won't register at once (ghosting)

On many membrane keyboards, certain combinations of simultaneous keys are dropped — a hardware limit called ghosting. Keyboards advertised with N-key rollover (NKRO) avoid this. Press several keys together to see how many your board reports at once.

AltGr also highlights Control

On Windows, AltGr is sent as Ctrl+Alt, so a phantom Control event accompanies the right Alt key. This is normal operating-system behavior, not a fault in your keyboard.

Function keys do something unexpected

Many laptops have an Fn-lock that swaps F1–F12 with media actions. Toggle Fn-lock (often Fn+Esc) if the function keys send the wrong codes.