title: Are there any DOM tree visualizers like Firefox's (defunct) 'Arboreal'?
body: <p>I beg pardon in advance if this is the wrong place to ask about tools, but I wasn't sure which other StackExchange site would be appropriate.</p>
  
  <p>I'm training some colleagues on HTML and basic CSS / jQuery selectors, and I feel it'd be very helpful for them to have an interactive DOM tree visualization - something with a broader, clearer view than the inspectors built into Firefox and Chrome.</p>
  
  <p>Years ago there was a Firefox extension called <a href="https://addons.mozilla.org/en-us/firefox/addon/arboreal/" rel="nofollow" title="Arboreal">Arboreal</a> that looks <strong>perfect</strong>, but it's long-since defunct. Does anyone know of a similar tool, ideally one that's interactive and built into the browser? Any browser is fine.</p>