Installing .NET changes MSIE User-Agent

by Marc Hedlund

Yesterday I installed the .NET SDK on my home machine. I had been playing around with User-Agent strings, the text a Web browser uses to identify itself to a Web server, for another project. Before installing .NET, my MSIE 5.5 User-Agent string was:



Mozilla/4.0 (compatible; MSIE 5.5; Windows NT 5.0)


After installing .NET, I noticed that the User-Agent string had changed to:



Mozilla/4.0 (compatible; MSIE 5.5; Windows NT 5.0; .NET CLR 1.0.2914)


This is nothing new, in that many companies have used User-Agent as the dumping ground for all sorts of nonsense for years. (In the example above, the string 'Mozilla' is a remnant of a time five years ago when some Web sites would show high-design content only to Netscape browsers -- which used Mozilla as a User-Agent string -- as these browsers supported non-standard HTML other browsers did not. Microsoft adopted the tag to avoid exclusion, and, well, it stuck.) It is interesting that the .NET CLR is advertised as though it were an operating system itself, which of course in a way it is.



So, are you interested in seeing how many of your site's visitors have installed .NET? Now you can know for sure! With a little JavaScript, you could even compare Java Plugin installs (which are installed with the Java SDK and Runtime) versus .NET installs and see market penetration for the two competing technologies.