Changelog - 2026-11-03

useElementSize no longer throws where there is no ResizeObserver

Bug Fix

In one line. useElementSize threw a ReferenceError in its effect on a host that has no ResizeObserver (an old WebView, some test hosts). It now stays at { width: 0, height: 0 } and observes nothing.

What changed

• No ResizeObserver, no throw. The effect checks for it before it observes. The hook returns 0 by 0, as it does before the first measure.
• Everything else is the same. A host that has ResizeObserver measures as before.

Who is affected

• An app that renders useElementSize on a host without ResizeObserver. The render no longer fails. Add a polyfill if you need a real size there.
• All other apps. No action needed.

See Hooks.