AOS

AOS is a lightweight JavaScript and CSS library for animating elements as users scroll through a webpage. It lets developers add animation behavior directly through HTML data attributes, making it easy to apply effects without writing custom JavaScript for every element. The library supports animations that trigger while scrolling down and can reset when scrolling back up. It includes options for duration, delay, easing, offsets, anchors, and once-only animation behavior. AOS is useful for landing pages, portfolios, marketing sites, and content-heavy pages that need subtle motion and visual rhythm. Its main value is providing scroll-based animation with a simple setup, flexible configuration, and broad front-end usability.