I\'m trying to find a (preferably open source) JS library to determine as much information as possible about the user\'s Web browser environment. I know it\'s possible to ge
You should definitely check out Panopticlick, an academic study (with detailed explanation on theory, and supporting data) to determine what makes a browser installation unique.
Panopticlick uses a slightly outdated version of this plugin detection script...
I maintain Common Feature Tests project, but it is merely a set of feature tests online, not a library. Feel free to use any of them on your page.
Sometimes I also use this simple test page for testing unknown environments (all tests there are really trivial one liners).