What are 2nd Party Cookies? Do they exist?
Someone recently asked me, “What is a 2nd Party Cookie”? Of course a smart person standing nearby overheard the question and was quick to answer, “There is no such thing as a 2nd Party Cookie.” After exploring the topic in more depth, we found the real question was actually, “What is 2nd Party Data?”
OK, so What is Second Party Data?
In the context of advertising, second party data implies sharing data or buying it from a “trusted partner.” This trusted partner collected first party data and now wants to sell or share it with you. An airline might be a trusted partner with a hotel. I know person ABC123 has purchased a flight every year in November to the same destination. Before next year’s flight is booked, that person might be interested in a discount for a new hotel recently built in that area. In many cases, there is a large agency or software vendor that can facilitate the sharing of someone’s first party data (now called 2nd party data) with another of their clients. 
In the context of large, multi-brand B2C corporations, second party data may just be a matter of sharing 1st party data from one brand with another. With a corporate data initiative in place, the parent company attempts to share the insights from their many visitors from one brand to get an extra lift for a new brand. The more popular brand collects 1st party data and then shares it for free with the other brand. The new brand now has additional “2nd party data” for increasing conversion rates and influencing more efficient ad spend.
Second party data is not new and Forrester had a paper in late 2014 on the topic. I think the reason it’s being talked about now is that people are actually attempting to use this “2nd party data” in the real marketing world. The technology to distribute this data has been there, but now, with better data collection in place (and tools such as Tealium’s Customer Data Hub) it’s easier than ever to take action on this data.
How to share visitor data between websites or domains
Services such as Gigya help add another level of visitor identification.  In addition to 3rd party cookies, you can leverage Tealium’s patented “stitching” technology that connects the dots for you when a user authenticates in some way. Tealium’s stitching technology also helps with Mobile Apps when cookies don’t really apply. 
Once your cross-brand data sharing is setup and your privacy policies are solid, then it may be time to branch out and look for other 2nd Party Data sources. Consult your favorite software company (Tealium) on how to make this happen.