Changelog - 2026-11-04

useIntersection tells whether an element is in view

New Feature

In one line. useIntersection({ target, rootMargin?, threshold? }) returns the latest IntersectionObserverEntry of the target, or undefined before the first one and where there is no IntersectionObserver. Read entry?.isIntersecting for the boolean.

The example is in useIntersection.

What changed

• The entry, not a boolean. It carries the ratio and the rectangles when you need them. The state changes only when isIntersecting or the ratio changed, so an unchanged entry does not render.
• The target is an element, a ref or null. It is read after every render, as for useResizeEffect, so an element held in state or mounted later is followed. A new element, rootMargin or threshold observes again from undefined.
• One threshold, no root. threshold is a single number; the viewport is the root, and rootMargin covers a scrolling root.
• Also in Ardor. Ardor.useIntersection joins the namespace, and ardor codemod namespace --hooks knows it.
• A new type. IUseIntersectionOptions is the options object, and TElementTarget is the type of a target, shared with useResizeEffect (it was TResizeTarget, unreleased).

Who is affected

• An app that keeps a hand-written IntersectionObserver to see whether an element is in view. You can use useIntersection instead and remove the observe, disconnect and server-render guard.
• All other apps. No action needed.

See Hooks.