Third party cookies
Last time, I posted an introduction to first party cookies. If you understand first party pixels, third party cookies should be pretty easy.
Like first party cookies, a third party cookie is some text that gets sent from a server to the user’s browser. However, the difference is that the server that sends the cookie isn’t the same server as the one that serves the requested page.
The diagram below shows one example of how third party cookies can work. Lets say that a user visits nytimes.com to read the news and sees a banner ad (lets say it’s a Pepsi ad). That banner ad is most likely being served by an ad server (lets say it’s Doubleclick) and not nytimes.com. When that ad gets served, Doubleclick’s ad server loads a cookie onto the user’s browser. It can do this because when the banner gets requested, it’s actually a Doubleclick server URL that gets requested, and it is at this point that the cookie gets loaded on the user’s browser.
A Doubleclick 1x1 pixel image can then be placed on other pages (most likely on some of Pepsi’s pages). When the user visits one of these pages, the browser will request the 1x1 pixel image, which will then request a Doubleclick URL. When the browser requests the Doubleclick URL, it will see that it has a cookie from that server and will send it along with the request.
Doubleclick’s server will then be able to connect the Pepsi page request with the original banner request (ideally a view on the Pepsi banner).
Interested in what some of these html tags might look like? Here’s a sample Atlas tag for a banner:
<iframe src="http://view.atdmt.com/AGI/iview/123/direct/01?click=" frameborder="0" scrolling="no" marginheight="0" marginwidth="0" topmargin="0" leftmargin="0" allowtransparency="true" width="160" height="600">
<script language="JavaScript" type="text/javascript">
document.write('<a href="http://clk.atdmt.com/AGI/go/123/direct/01/" target="_blank"><img src="http://view.atdmt.com/AGI/view/123/direct/01/"/></a>');
</script><noscript><a href="http://clk.atdmt.com/AGI/go/123/direct/01/" target="_blank"><img border="0" src="http://view.atdmt.com/AGI/view/123/direct/01/" /></a></noscript></iframe>
If you’re familiar with html and or javascript code, you can see that this code makes a request to atlas’ servers – view.atdmt.com. The iframe tag will basically load an entire Atlas page within the 160x600 specified dimensions.
Here’s an example of a 1x1 pixel:
<script>document.write('<s'+'cript language="JavaScript" src="http://switch.atdmt.com/jaction/xyz"></s'+'cript>')</script><noscript><iframe src="http://switch.atdmt.com/iaction/xyz" width="1" height="1" frameborder="0" scrolling="No" marginheight="0" marginwidth="0" topmargin="0" leftmargin="0"></iframe></noscript>
You can see that the width and height of this image are both one pixel. As mentioned above, the image calls an Atlas URL, in this case http://switch.atdmt.com/iaction/xyz