Technically Node 4 is io.js 4 after Node 0.12 was merged into io.js 3.<p>So it&#x27;s really 0.11.x -&gt; 1.x -&gt; 2.x -&gt; 3.x -&gt; 4.0.0. Except that 1.x, 2.x and 3.x weren&#x27;t called &quot;Node&quot; at the time because Joyent owns the trademark and went on to release their own 0.x release(s) until the merge happened.