BackendInfo is a lightweight (24kb) Firefox extension that detects name and version of backends behind websites
Detecting 15 different backends / 130+ versions
Drupal 6.x, 5.x, Wordpress 2.x
phpBB 2.x, 3.x, Django, DokuWiki
MediaWiki, MoinMoin, Reddit, Blogger, Joomla, and more
BackendInfo basically works by detecting URLs, strings and regular expressions. This ranges from typical html and css codes to certain directory and file-structures. It is easy to track changes in css, js and html files between releases that can be used to identify the backends exact version with tools like Meld. Furthermore, documents like CHANGELOG, UPDATES, etc are often left readable after a standard backend installation, providing some more insight as well.
BackendInfo is a “plugin framework”, every extension checks for a given backend by required URLs, and optionally a number of strings or regex patterns that have to be contained or not contained in this url.
Get BackendInfo from : http://www.backendinfo.com