What is first-party vs second-party vs third-party data?

First-party data is what you collect directly from your own audience. Email addresses, purchase history, website behavior, stated preferences. You own it. You control it. It's the most reliable and privacy-compliant source.

Second-party data is someone else's first-party data that they share with you through a partnership. A co-marketing arrangement, a data sharing agreement, an integration with a complementary brand. You don't own it directly, but you have legitimate access.

Third-party data comes from aggregators who compile information from many sources and sell it. Demographic enrichment services, intent data providers, data brokers. You're buying access to data you didn't generate.

The hierarchy of trust follows this order. First-party is most accurate because you observed it. Second-party can be valuable if the partner has similar audiences. Third-party is often stale, inaccurate, or collected without proper consent.

Privacy regulations like GDPR and CCPA have made third-party data riskier. First-party data strategies are now essential. Build your segmentation on what you know directly, and treat external data as supplementary at best.