This is a good one!  I was talking to a consultant the other day who asked me if I had every heard of the Universal Cookie?  He said that Ad Server “A” and “D” were both boasting about having a Universal Cookie that could readily pass data about the ad serving through to site optimization and/or site analysis software.

I had to struggle with this one for a couple of minutes while we spoke as it questioned the technical plausibility of domains and cookies.  I asked some additional questions and shared my knowledge and here is what came out of our discussion.

Ads are served from a specific domain, http://www.domain.com/.  Cookies are written and read specifically from that domain, .domain.com cookie.  An ad servers can only read and write their own cookies and a sites can only read and write their own domain-named cookies.  One domain-named site or ad server can not access the information stored in the cookie of another domain name.  So ad server D can not expose the information stored in the .D.com cookie to its advertisers.  An advertiser could never just read the information stored in that cookie.  Only the D.com domain servers can read that cookie.  The Ad Server would have to expose the data, convert it to a usable form and then share it.  None of this can happen in real time.

So what was this guy talking about?  A search on Google for Universal Cookies came up with only a few threads and they were pretty dated.  People talked of the concept and of how such a thing would be great for overcoming the high-level threat to the persistence of third party cookies.  But the plausibility of a Universal Cookie is not there.  This appears to be another misuse of naming convention for the same old bag of tricks.

The only thing that these ad servers could possibly be offering is a historical, and likely expensive, data synchronization between the information stored in their third-party cookie and the advertiser, site optimization software or site analysis software.  Somehow the data needs to normalized and synchronized, unlocked if you will.  So its not that their cookies are universal, its just that they are converting the data to a format that can be used.  Historical information is useful but its got its limitations.  You can only make future decisions on it, not reactive ones in the moment.  Most, and I mean like almost ALL advertisers are not at this level of sophistication of analysis.

A few of the largest ad servers have done this for a couple of years, with the largest eCommerce sites on the markets.  It has proven to be a laborious, expensive and not very accurate process.  The advertiser sends anonymous customer data to the ad server who then synchronizes it with normalized anonymous ad serving data.  The result is a new profile of segment data that represents acqusition-marketing insight into customer types. 

Bottom line is that the data locked up in a third party cookie is just that, locked.  Exposing it has only some benefit to the advertiser.  But it is clearly not through any type of universal cookie.

There is another way.  If ads are served out of the same domain name as the advertiser’s domain, then the cookie data on the browser’s compute is readily available to be read by the advertiser, their site optimization software or site analysis platform.  This is to be known as first party ad serving. 

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