Category taxonomies value 1 means IAB Tech Lab Content Category Taxonomy 1.0

When to send it

Value 1 names the first IAB content category list, whose IDs look like "IAB1" or "IAB25-3". OpenRTB 2.5 and earlier printed those codes directly in the specification, which is why so many bcat blocklists and cat arrays still use them. AdCOM marks the taxonomy deprecated because it has no sensitive-category flags, and advises against using it.

It is nevertheless the default for every cattax field (BidRequest.cattax, Site.cattax, App.cattax, Publisher.cattax, Content.cattax, Producer.cattax and Bid.cattax), so a buyer that sees no cattax assumes 1. Some contracts accept nothing else: rtblint's Commerce Grid supplier profile allows only BidRequest.cattax 1. The usual confusion is with 2. Both are content taxonomies, but 2.0 replaced the IAB-prefixed codes with numeric IDs, so no single ID string is valid in both.

Example

{
  "app": {
    "cattax": 1
  }
}

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.