unstable_useViewTransitionState

declare function unstable_useViewTransitionState(
  to: To,
  opts: { relative?: "route" : "path" } = {}
): boolean;

type To = string | Partial<Path>;

interface Path {
  pathname: string;
  search: string;
  hash: string;
}

This hook returns true when there is an active View Transition to the specified location. This can be used to apply finer-grained styles to elements to further customize the view transition. This requires that view transitions have been enabled for the given navigation via the unstable_viewTransition prop on the Link (or the Form, navigate, or submit call).

Consider clicking on an image in a list that you need to expand into the hero image on the destination page:

function NavImage({ src, alt, id }) {
  let to = `/images/${idx}`;
  let vt = unstable_useViewTransitionState(href);
  return (
    <Link to={to} unstable_viewTransition>
      <img
        src={src}
        alt={alt}
        style={{
          viewTransitionName: vt ? "image-expand" : "",
        }}
      />
    </Link>
  );
}