Data & identity · also called Segment, audience
Audience segment
An audience segment is a group of people or devices defined by shared characteristics, such as demographics, interests, purchase behaviour or intent, used to target or measure advertising.
Instead of targeting every person, advertisers target groups: "new parents", "in-market for SUVs", "lapsed customers", "sports fans in Mumbai". Each group is an audience segment, built from data about who people are or what they have done.
Segments can come from first-party data (a brand's own customers), publishers (seller-defined audiences), retailers (retail media shopper audiences), or third-party data providers. They may be built from declared data, observed behaviour or modelled predictions, including lookalikes. The IAB Tech Lab Audience Taxonomy provides common names for segments so buyers and sellers can speak the same language.
Segment quality varies. Accuracy, freshness, scale and how the segment was built matter greatly; some third-party segments are based on thin signals. Privacy law also limits certain segments: targeting based on sensitive categories such as health, religion or sexuality is restricted under GDPR, the EU's Digital Services Act prohibits platforms from targeting ads using such data, and targeting minors is increasingly banned.
Think of it like this
An audience segment is like a guest list for a themed party: people chosen because they share something relevant.
An example
A running-shoe brand in Kenya targets a segment of 250,000 people who bought sportswear in the past six months from a retailer's loyalty data.
Related terms
Lookalike audience
A lookalike audience is a group of new people who statistically resemble an advertiser's existing customers or best users, found by a model to extend reach beyond known contacts.
Behavioral targeting
Behavioral targeting shows ads to people based on their past online behaviour, such as sites visited, searches, purchases or app use, collected over time and often across different services.
Third-party data
Third-party data is information about people collected by companies with no direct relationship to them, then aggregated and sold or licensed to advertisers, often as ready-made audience segments.
First-party data
First-party data is information a company collects directly from its own customers or audience, such as purchases, sign-ups, app use and site behaviour, through its own channels.
Seller-defined audiences
Seller-defined audiences (SDA) is an IAB Tech Lab specification that lets publishers label ad requests with standardised audience segment IDs from their own data, without passing personal identifiers to buyers.
Sources: IAB Tech Lab Audience Taxonomy, European Commission: Digital Services Act