CSS content-visibility

Provides control over when elements are rendered, so rendering can be skipped for elements not yet in the user's viewport.

IntersectionObserver

API that can be used to understand the visibility and position of DOM elements relative to a containing element or to the top-level viewport. The position is delivered asynchronously and is useful for understanding the visibility of elements and implementing pre-loading and deferred loading of DOM content.

css property: content-visibility