The IAB Tech Labs seller-defined audiences specification is among many, many digital ad industry efforts to displace the third-party cookie with purportedly privacy-friendly alternatives. Its effectively a cohort-based targeting method packaged with a nutrition label for the corresponding ad targeting data.
Rather than a publisher sharing person-specific identifiers like cookie-based IDs or email addresses with advertisers, audiences are organized into groups predicated on categories like demographics, interests and buy intents using IAB Tech Labs Audience Taxonomy standard. And advertisers can check the makeup of the seller-defined audiences by referencing the corresponding data transparency label that outlines who provided the audience data, what the audience segment is, the way the segment was compiled and what the underlying databases is.
However, because the name seller-defined audiences implies, publishers come in charge of establishing these audience segments. It has turn into a reason behind consternation among advertisers and agencies because some publishers might define exactly the same audience differently than others or differently when compared to a marketer, as outlined in the video skit above.