True, the v1 used internal API directly. They ported it to a newer API that is also used by Developer Tools.<p>Though even today, I prefer Firebug as I really like the good UI and it has several features that are nowhere to be found in neither Developer Tools in Firefox nor DevTools in Chrome nor F12 in IE11.<p>E.g. the &quot;DOM&quot; tab that let&#x27;s one to view the DOM state - it&#x27;s like working with Smalltalk&#x2F;Squeak and its object browser window.