keydowns

Keydown is a keyboard event emitted by a user interface when a key is pressed down. In modern browsers and many graphical user interfaces, keydown is one of the primary keyboard events used to detect user input. The plural form, keydowns, is sometimes used informally to refer to multiple such events occurring over time.

Unlike a simple click, a keydown may repeat if the user holds the key, a behavior known as auto-repeat. It typically fires before the key's character is produced, especially for non-character keys, and it often precedes a keyup event when the key is released. Some environments also fire a separate keypress event, but keydown remains a fundamental and more widely supported signal.

The event object is a KeyboardEvent and contains information such as the key value (key), the physical key on the keyboard (code), and modifier flags (altKey, ctrlKey, shiftKey, metaKey). Older code may reference keyCode or charCode, but those properties are deprecated in favor of key and code. A repeat boolean indicates whether the event is part of an auto-repeat sequence.

Handling involves registering a listener for the keydown event, typically via addEventListener in web contexts. The handler can inspect event.key or event.code, read modifier flags, and optionally call preventDefault to suppress the browser’s default action. Debouncing or guarding against repeated triggers is common when handling long presses.

Cross-platform and cross-browser differences exist in the exact values of key and code, and in how non-printing keys are represented. In modern web development, keydown and keyup are preferred for reliable capture of keyboard input, while the deprecated keypress is ignored in many environments. Other GUI toolkits offer analogous keydown events with similar semantics.

See also keyup, keypress, event handling, KeyboardEvent.