`key` follows layout and modifiers
The value can be `a`, `A`, `@`, or a named key depending on keyboard layout and Shift or AltGraph state.
`code` describes physical position
A physical letter position can report `KeyQ` even when another layout produces a different character there.
Repeat marks held keydown events
After an initial keydown, the operating system may emit repeated keydown events until keyup.
Some shortcuts belong to the browser
Operating-system and browser combinations may never reach the page or should not be blocked for safety and accessibility.
Modifiers and composition add context
A keydown record includes the active Ctrl, Alt, Shift, and Meta state so the same physical code can be interpreted in context. International input methods may compose several events into one visible character, dead keys can report a named logical value, and browser or operating-system accessibility features can transform input before the page sees it. This tester displays delivered KeyboardEvent evidence only. It does not read raw USB reports, firmware scan codes, text entered in other controls, or events after the marked surface loses focus.
Use keyup to investigate an apparent stuck key
A normal press produces an initial keydown, optional repeated keydowns while held, and a keyup when released. If focus moves away before keyup arrives, the page clears its held set rather than falsely claiming hardware failure. Refocus, press the suspect key alone, and watch both event types. A persistent missing release across another browser and another computer is stronger evidence than one interrupted test. Exported logs remain local tab-separated text and may contain typed characters, so review them before sharing.