What’s My User Agent?
Have you ever wondered what your user agent is? Did you also have some sleepless nights because you couldn’t find it out? Now it’s over! Just visit the site http://whatsmyuseragent.com/ and it tells you everything.
Example: my current user agent is
Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:11.0) Gecko/20100101 Firefox/11.0
(The image was borrowed from http://whatsmyuseragent.com/WhatsAUserAgent.asp.)
But… should I care about it?
In some cases yes, you should care about your user agent. For instance, if you want to fetch some web pages with a Python script, you can have some troubles. The Python script identifies itself as a Python agent, and some sites simply block them :( But, of course, we cannot be tricked so easily. Just change the default user agent in your Python script and enjoy the free ride :) For more info, refer to this article.
See also http://www.user-agents.org/, which is a searchable database of user-agents as used by browsers, search-engines spiders and crawlers, web-directories, download managers, link checkers, proxy servers, web filtering tools, harvesters, spambots, badbots.
There is also an interesting Firefox plug-in that allows you to change your user-agent.
History of the browser user-agent string (update 20120425)
Have you ever wondered why user-agent strings are a complete mess? Here is the story.