Implementing scroll-aware UI state with CSS

In February 2025, new CSS features like scroll-state and animation-timeline were introduced, enabling developers to create scroll-aware UI elements that enhance user experience by responding dynamically to scrolling actions without relying heavily on JavaScript. These features offer solutions for implementing scroll-driven animations and styles, such as parallax effects and sticky navigation bars, using CSS instead of JavaScript to optimize performance and reduce main thread workload. However, browser compatibility issues persist, as these features are only supported in some browsers, necessitating the use of JavaScript polyfills to maintain cross-browser functionality and accessibility. Despite these limitations, scroll-aware UI designs can significantly improve webpage interactivity and user engagement, offering endless possibilities for creative and efficient web development.