keyupevent

KeyUpEvent refers to the moment a user releases a key on the keyboard. In web environments, this is exposed as the keyup event, which fires on the element that currently has focus when the key is released.

The event object provides details about the key interaction, including key (the character or key name, such as "Enter" or "a"), code (the physical key location, such as "KeyA" or "Enter"), location (keyboard key location), and modifiers such as ctrlKey, shiftKey, altKey, and metaKey. It also includes repeat (true if the key is being held down and repeats) and isComposing (true during IME input). Time and target information are available via timeStamp and target properties.

KeyUpEvent is distinct from keydown (fired when a key is pressed) and the historical keypress (which is largely deprecated). It is commonly used for end-of-key actions, such as validating input after the user finishes typing, triggering autocomplete, or handling keyboard shortcuts that should execute when the key is released. Developers may debounce keyup handlers to avoid excessive processing.

Across platforms, the concept exists beyond the browser: in Java, KeyEvent.KEY_RELEASED represents a key release; in C# and .NET, the KeyUp event serves a similar role. The terminology and exact properties vary by framework, but the underlying behavior—detection of key release—remains consistent.

See also: keydown, keypress, input events.