Tracking banners and other outgoing links – AutomaticallyGoogle Analytics specific, Plugins & Hacks August 15th, 2007
[This hack is for the legacy urchin.js tracking code.
Always refer to the Scripts & Downloads section for the latest version.]
April 2011 – New async hack launched
This hack has been completely revise for the latest GA async code. Further info >>
The script works by looking for links within the browser’s Document Object Model (DOM) that do not match the domain value given in the variable array extTrack. If the link does not match extTrack then it is considered an external link and so is modified to include the urchinTracker call. By this method, all external links will show in the Google Analytics reports as:
A note on performance: Each time your page loads, this script will go through all links referenced on the page to see if it is external. Clearly the more links on your page, the harder the script must work. As long as the number of links on each page number in the hundreds and not thousands, performance should not be a problem.
Also note that for pages with a large number of links, it is possible that visitors will click on an external link before the script has modified it. The result is that click through will not be tracked by Google Analytics which is an accuracy consideration that effects all web analytics vendors.
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