Does anyone know what tumblr is written in? I have been trying to figure it out.
It's PHP...
I wonder if the Tumblr guys are using a framework or if it is all home brew.
Both: it’s a homebrew framework to add MVC structure and a useful secondary function library to PHP 5 that we started in 2006 and have constantly evolved into a very finely tuned framework for our needs. The same framework runs some of Davidville’s former consulting-client sites as well as all of my personal sites and projects. It’s not available publicly anywhere, but we may release it in the future.