Glossary
Second-party data
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Second-party data is another organisation's first-party data that you obtain directly from that organisation, under an agreement and for an agreed purpose, rather than buying it from a data marketplace.
The term only makes sense next to its neighbours. The IAB Tech Lab defines first-party data as data an organisation acquires from people's interactions with it, online or offline (IAB Tech Lab, Data Clean Rooms Guidance, v1.0). When that organisation shares it directly with a named partner, the partner holds second-party data. Third-party data, by contrast, comes from companies with no direct relationship with the people involved.
Typical pairs are a retailer and a brand, an airline and a hotel group, or a publisher and an advertiser. The same guidance lists "audience expansion" with first- and second-party data among clean room uses. Clean rooms let partners match and analyse each other's data without copying it across. The data's origin is known, which is the main advantage over bought segments. Scale is the limit, and so is the law: each sharing needs a lawful basis, clear notice and a contract that fixes the purpose.
Example: An airline and a hotel group load their loyalty members into a clean room. They find 300,000 shared members who flew to Lisbon in the past year but booked no hotel there. The hotel group targets that segment, and neither side copies the other's member list.
Related terms: third-party data, clean room, PAIR, data processing agreement, joint controller, CDP.