Very nice. It reminds me of a similar all-in-browser file transfer tool I built ages ago called nearshare. This was WAY before webrtc was a thing so my approach was to actually run a web server in the browser via a java applet. :)
Does obsolete mean deprecated or removed?
It used LiveConnect[0] to talk to the UI-less java applet[1] hosting the web server. It was a weird (and therefore kind of fun!) combination.