z"/>
      </svg></a> </h3>
<section aria-labelledby="toc_preventing-transitions-via-willtransition">
<p>When a transition is attempted, whether via <code>{{link-to}}</code>, <code>transitionTo</code>,
or a URL change, a <code>willTransition</code> action is fired on the currently
active routes. This gives each active route, starting with the leaf-most
route, the opportunity to decide whether or not the transition should occur.</p>
<p>Imagine your app is in a route that's displaying a complex form for the u