Keycode tester

How to use the keycode tester

1. Press any key. The large box shows the key value and the fields beside it show event.key, event.code, event.keyCode, event.location, held modifiers, lock keys that are on, and event.repeat.
2. Press Start full capture to also inspect keys the browser normally uses itself, such as Tab, Space, F-keys and many shortcuts. Press Esc twice quickly, or Stop, to exit.
3. Open the event log to see the last 80 keydown and keyup events in order, for example to check a key combination.
4. Press Copy last event (JSON) to paste the values into a bug report or code. Clear log empties the list.

What each value means

• key: the character or key name produced, after layout and modifiers. Shift+2 gives "@" on a US layout and '"' on a UK layout.
• code: the physical key, named after its position on a US QWERTY keyboard. On a French AZERTY keyboard the key labelled A reports KeyQ. Use it for game controls and shortcuts tied to position.
• keyCode (and which in the JSON): legacy numbers that are deprecated but still reported. They differ between layouts and browsers; prefer key or code in new code.
• location: 0 standard, 1 left, 2 right, 3 numpad. It tells left from right Shift, Ctrl, Alt and Meta, and keypad keys from the number row.
• Modifiers and lock keys: Control, Shift, Alt and Meta held during the event, and whether Caps Lock, Num Lock or Scroll Lock is on, as reported by getModifierState().
• repeat: yes for auto-repeated events while a key is held.

Common surprises

• Dead: accent keys on many international layouts produce no character until the next key, so key is Dead.
• Process or keyCode 229: an input method (for example for Chinese or Japanese, or some phone keyboards) is composing text and the real key is hidden.
• AltGr on Windows usually arrives as Control plus Alt, so you may see two events and both modifiers.
• Mac Command key: while Command is held, the browser does not report key releases of other keys.
• Empty code or Unidentified: the keyboard, driver or remote session did not supply a physical key. The Fn key never appears at all because it is handled inside the keyboard.

Limits

The page shows what the browser exposes, after the operating system and keyboard layout have processed the key. It cannot show raw scan codes or USB HID data, cannot see keys the operating system takes first (such as Ctrl+Alt+Del), and does not change or remap keys. It also does not measure keyboard latency or polling rate. To check that every key on a keyboard works, use the keyboard test; for several keys at once, the ghosting test.