Category taxonomies value 5 means IAB Tech Lab Content Taxonomy 2.1

When to send it

Value 5 selects Content Taxonomy 2.1. It belongs in the content-side fields (Site.cattax, App.cattax, Publisher.cattax, Content.cattax and Producer.cattax), and it can also describe ad categories in BidRequest.bcat or Bid.cat when both parties classify ads with the content taxonomy.

Buyers with a 2.x mapping can read the IDs directly. The confusion is with 2 (Content Taxonomy 2.0, deprecated) and 6 (Content Taxonomy 2.2). IDs overlap across the 2.x files, but nodes are added and retired between versions, so name the exact file your classifier uses.

Example

{
  "app": {
    "cattax": 5
  }
}

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.