YouTube is developed on PHP or .NET ?

[sk89q]

I built a YouTube Flash player back in the day when YouTube was all new (it was a really badly designed player to embed back then). All their URLs ended in .php. Some months later after I started this player, YouTube gradually removed the .php extensions, removing the .php extension off the internal things last (i.e. the ones that loaded the movie). Though, even now, look: http://www.youtube.com/watch.php?v=nsCXZczTQXo - I would presume YouTube's frontend is largely written in PHP then, *unless* they really rewrote all their code, doubtfully. The backend stuff is not in PHP though, I hear. It is written in Python.

Facebook is largely in PHP.