Category taxonomies value 4 means IAB Tech Lab Audience Taxonomy 1.1

When to send it

Value 4 names Audience Taxonomy 1.1. AdCOM includes it so one enumeration can identify content, ad product and audience vocabularies alike. The OpenRTB 2.6 fields that take a cattax all describe content or ads, so 4 has no natural home in them.

Audience segments in OpenRTB 2.x travel in User.data segments, and their taxonomy is signaled with a segtax value in the Data object's ext, not with cattax. A seller that sends 4 in Site.cattax is almost certainly mislabeling content categories. Do not mix 4 with the content taxonomies (5, 6, 7 and 9), because the IDs mean different things.

Example

{
  "app": {
    "cattax": 4
  }
}

Fields that carry it

• app.cattax
• seatbid.bid.cattax
• cattax
• app.content.cattax
• app.content.gtax
• app.content.producer.cattax
• app.publisher.cattax
• site.cattax

Other values in category taxonomies

The category taxonomies list page explains the whole list and its common mistakes.