Keyboard Test

A keyboard test checks whether key presses are reaching the browser and shows how the browser describes each key event. It helps diagnose cases where a key feels stuck, a shortcut does not work, a laptop keyboard may be damaged, or a new mechanical keyboard needs a quick sanity check. The tool displays practical event data such as key, code, legacy keyCode, key location, repeat state, and modifier keys like Ctrl, Shift, Alt, or Meta. This helps separate hardware problems from layout or software behavior: a physical key position can be reported differently from the character it produces. Browser tests cannot capture operating-system shortcuts such as Ctrl+Alt+Del or Alt+Tab, so absence of those events is normal rather than a keyboard failure.

The browser surfaces keyboard events through the KeyboardEvent interface: each press fires a keydown and a keyup event. KeyboardEvent carries several key properties: key is the character value of the key (affected by layout and Shift state - e.g. a vs A); code is the physical position identifier (layout-independent - KeyA is KeyA on both QWERTY and AZERTY); keyCode is a legacy numeric value (deprecated but still seen in older code); location indicates the key's position (0 standard, 1 left, 2 right, 3 numpad). To detect combinations, listen to the four boolean modifier flags ctrlKey, shiftKey, altKey, metaKey - e.g. on Ctrl+C, ctrlKey=true and key='c'. The firing order is keydown -> keypress (deprecated) -> keyup; while a key is held, keydown keeps firing and event.repeat=true. Game development prefers code (immune to the player switching layouts), while input fields prefer key (which gives the actual character). N-key rollover (NKRO) means the keyboard hardware can register any number of keys simultaneously; ordinary USB keyboards are limited to 6KRO by the USB HID protocol - more than 6 keys held at once starts dropping events. Mechanical keyboards with PS/2 interfaces or specialized drivers can deliver true NKRO.

• KeyboardEvent.key is the character value ('a'/'A'/'Enter'), affected by layout and Shift - use it in input field scenarios.
• KeyboardEvent.code is the physical position identifier ('KeyA'/'Digit1'), layout-independent - use it for games and shortcut bindings.
• location values: 0 standard, 1 left modifier, 2 right modifier, 3 numpad - useful when distinguishing left/right Shift, Ctrl, Alt.
• Combinations: ctrlKey/shiftKey/altKey/metaKey are four booleans indicating modifier state; combine with key to detect Ctrl+C, Cmd+Shift+P, etc.
• event.repeat=true means a held key is auto-repeating; in long-press tests, use this flag to filter out repeated events.
• 6KRO vs NKRO: 6-key rollover is a USB HID protocol limit; mechanical keyboards can reach N-key rollover (NKRO) through PS/2 or a dedicated driver.