InertiaScrolling

InertiaScrolling is a user interface technique where scrollable content keeps moving briefly after the user ends a drag, gradually slowing to a stop. The effect imitates physical momentum and helps users perceive the relationship between their actions and the content’s movement.

Mechanism: The system measures the velocity at release and applies a deceleration over time, updating the scroll position in small steps until velocity reaches zero or content bounds are hit. Some platforms also allow a bounce at the edges.

Implementation: On mobile devices, momentum scrolling is typically provided by the native engine in the OS or browser. For custom scroll areas, developers can rely on native behavior or implement a physics-based scroll using JavaScript with requestAnimationFrame. Performance and consistency are important concerns, and developers must balance smooth motion with resource use on lower-end devices.

Considerations: Inertia scrolling can improve perceived responsiveness but may affect accessibility or predictability. Respect reduced-motion preferences, ensure keyboard navigation remains reliable, and provide a way to halt motion. If used with snapping or boundaries, tuning deceleration and boundary behavior is important to avoid jank or disorientation.

History and terminology: Momentum scrolling is a common term describing this behavior in mobile browsers and platforms. InertiaScrolling is used in documentation and libraries to refer to the same concept. There is no universal standard API for inertial scrolling; implementations depend on the platform or on custom code.