Whenever we find interesting Web pages via Rss or aggregators like Google Reader, our natural reaction is to signal them to all our friends and colleagues who may be interested. Sometimes we do this by sending the same links to those pages that we found in the aggregator or Rss reader via email. Other popular options are pasting the links on our Facebook wall or feed them to some URL shortener for Twitter.
Now, did you ever stop to look at how those URLs you republish or email are built? Have you ever noticed that, very often, they are (much) longer than they should be? For example, many URS received by news aggregators look like these (please add more real life examples in the comments!):
The part in bold is not part of the URL, meaning that you don’t really need it in order to load those Web pages. Those are codes that Webmasters and online advertisers add to track as exactly as possible where, or from who, their visitors came to know about their page, who their contacts are and so on.
For example, if Joe Smith finds an article through Google Reader (which fed it to Joe with a unique code attached to the URL) it’s obvious that whoever reaches that page using the address with that same code got it, more or less directly, from that Joe Smith.
Nothing tragic here, of course. It’s just something that’s useful to know, both to have a better idea of how many different ways exist to track people online(**) and to know what you should remove from a URL before republishing it, if the idea of contributing to tracking bothers you.
(**) did you know, for example, about browser fingerprints?