pointerId

PointerId is a numeric identifier used by the Pointer Events API to distinguish individual input pointers, such as mouse, pen, and touch contacts, within a single document. It is exposed as the pointerId property of PointerEvent objects and uniquely identifies the pointer that caused a sequence of events.

The value is stable for the duration of a pointer’s contact with the surface. All events belonging to the same pointer (for example, a finger touching and then moving across a touch surface) carry the same pointerId, while different pointers receive different IDs. In practice, new pointers are assigned new IDs, often starting from 1 and incrementing with each new contact; the exact sequence is implementation dependent.

PointerId is scoped to the current document and session. It is not guaranteed to be persistent across page reloads, cross-origin contexts, or device changes. It should not be used as a persistent reference to a user or device, but rather as a runtime handle for coordinating multiple simultaneous pointers within a single page.

Practical uses include tracking multiple concurrent pointers to implement multi-touch gestures, dragging operations, or gesture recognition. pointerId is also required for pointer capture, where an element can receive pointer events even when the pointer moves outside the element’s hit area by calling setPointerCapture(pointerId).

Compatibility notes: pointerId is part of the Pointer Events API, supported in modern browsers. Some older environments rely on legacy touch or mouse events; feature detection is recommended when targeting older platforms.