The web platform is evolving, introducing powerful new primitives that change how we build interfaces. Among these innovations is the toplayer—an important yet often misunderstood rendering concept. This talk explores the toplayer rendering mechanism, learning how it enables UI patterns and examining its role in accessibility, performance, and developer experience.

The toplayer isn't just another technical specification—it represents a shift in how browsers handle elements that need to break out of the normal document flow. From dialog elements to the new popover API, custom tooltips to modal interfaces, the toplayer has quietly become essential for creating modern web experiences. By understanding how the toplayer works, developers can build more robust, accessible, and maintainable components while avoiding common pitfalls that lead to inconsistent user experiences.

In this session, we'll dive into the toplayer to understand how browsers handle stacking contexts, painting order, and focus management within the toplayer. Through practical examples and live coding demonstrations, attendees will gain both theoretical understanding and practical skills they can apply to their own projects.