Google tracking outbound links from searches

I’ve never realized but Google use your browser in such a way it tells them which link you followed out from the search results. Searching for “damieng” for example will show my home page as the first result. The browser window will show but click on it with JavaScript enabled and instead you’ll go somewhere like;

Let’s break this down:

  1. (their tracking and redirect page)
  2. sa=t (“t” for normal search area, “l” for right-hand sponsored results)
  3. ct=res (“res” for normal results, “pro” for sponsored results above normal results)
  4. cd=1 (result number for normal results, a unique code for sponsored results)
  5. url=http%3A// (the HTTP encoded version of where you were going)
  6. ei=yMf5QoHUJczcQr-YvfAN (a base-64 encoded request number, no doubt tied to what I searched for)

Google’s page then returns a “302 Not Found” and tells your browser that page can be found at

Google have apparently been doing this on and off for some time.

It is telling that they have gone to the trouble of hiding the tracking link by using JavaScript when they could just have linked directly to their tracking pages… but then that would have given the game away to anyone copying the links or looking at their status bar I guess…

If you want to see all this for yourself either view the source or try out the excellent Live HTTP Headers extension for Firefox.


1 responses

  1. Avatar for Lemon

    I was snooping my net traffic when I came across the Google tracking link. Overall I am more surprised at the fact they have cleverly disguised the tracking using the JSONRequest technology (Strangely Firebug does not pickup the XMLHTTPRequest) I also noted when logged into Gmail the URL’s are changed into 302 Redirects..? Its not to stop automated requests (copying links) But to purely gain from the ‘free’ search engine they offer. PS: This is the only site iv found discussing this topic, So.. Well done! Lemons

    Lemon – May 1st, 2008