Visual display of tracking cookies - collusion

Thanks to the Guardian I've come across a Firefox plugin which gives you a visual display of tracking cookies. It's called Collusion. (Update 20 March 2021 It's now Lightbeam. Thanks to someone at Comparitech.com for telling me about this broken link.)

I've been vaguely aware that website were passing information to each other, as I noticed that if I visited crucial.com to look at memory then I'd see more Crucial adverts on other sites. Similarly with Dell. Then one day I found a link on a site next to an advert (unfortunately I didn't note it down) which gave more information on why I was getting these Crucial adverts. It was easy to understand and very upfront about how it used information from other sites to display relevant adverts.

Here's what you get if you visit the following sites:

• crucial.com
• dabs.com
• ebay.co.uk
• bucksfreepress.co.uk
• guardian.co.uk

Each circle represents a site that places cookies in your browser and a line means that the site at one end placed a cookies for the site at the other end of the line.

The most circles appeared when I visited bucksfreepress.co.uk (one of the red squares with a yellow i in the middle). I guess it's a sign of a struggling industry that it has to try so hard to be clever with its advertising.