Third-party data is data collected and aggregated by outside providers, then sold for targeting, with no direct relationship to the customer.
Category
Data Types
Also known as
3rd-party data
It was the fuel of the DMP era. Privacy law and browser changes made it less reliable and more regulated, pushing marketers toward first-party approaches. Browsers diverged rather than converged (Chrome kept third-party cookies in 2025 while Safari and Firefox block them), so the move to first-party is driven by regulation and reliability, not one vendor’s decision.
In practice
Third-party data still has uses, but it is usually a supplement now, not a foundation. Before you rely on a source, ask for its provenance and legal basis in writing; if the vendor cannot produce them, that is your answer.
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