Third-Party Data

Third-party data is audience data sourced from outside the advertiser and the publisher — typically licensed from a data broker (Acxiom, LiveRamp, Experian, Bombora, Lotame). The data describes people the advertiser hasn't directly interacted with, mapped to identifiers (cookies, mobile IDs, hashed emails) that can be used to target impressions.

Third-party data was the dominant audience layer in programmatic from ~2010 through ~2020. The shift to identity deprecation — Apple's IDFA opt-in (2021), Google's third-party cookie removal (delayed but ongoing), browser tracker controls — has reduced third-party data's addressability dramatically. By 2026, third-party-data revenue at major brokers had fallen 30-50% from 2020 peaks.

The replacement isn't a single thing. First-party data activated through clean rooms is gaining share for high-value retargeting. Contextual targeting (matching content rather than user) has come back for upper-funnel reach. Cohort-based ID-less methods (Privacy Sandbox, FLEDGE, Permutive) are absorbing some demand. And for DOOH and CTV specifically, sensor-based audience signals (Trillboards' cohort composition, T-Vision's CTV audience panel) replace the third-party-data role wholesale.

Third-party data still has a role in B2B (Bombora-style intent), in less-deprecated identity environments (CTV pre-deprecation), and in panel-based audience modeling. But it's no longer the default audience layer.