Site.cat

Content categories for the whole site, as an array of taxonomy IDs. The taxonomy is named by Site.cattax; when that is absent, IAB Content Category Taxonomy 1.0 applies.

Currentstring arrayOptionalSince 2.0

Field facts

Path: site.cat
Object: Site
Type: string array
Requirement: Optional
Added: OpenRTB 2.0
Spec section: 3.2.13

How it is used

Before 2.6 the spec pointed straight at the IAB 1.0 category list, so older traffic carries IDs such as IAB12 for news. If you send Content Taxonomy 2.x or 3.x IDs, set Site.cattax to match, or buyers will look them up in the wrong list. Site-wide categories are coarse; Site.sectioncat and Site.pagecat describe where the impression actually is.

Example

Where the field sits in a payload, with everything else left out:

{
  "id": "req-1",
  "site": {
    "cat": [
      "IAB12"
    ]
  }
}

Common mistakes

Free-text values such as "News" or lowercase "iab12" match nothing in any taxonomy, so buyer category filters ignore them.
Sending Content Taxonomy 3.x IDs without Site.cattax. Buyers read them against the 1.0 list, where numeric IDs such as "483" do not exist.

Version history

Added in OpenRTB 2.0, and present in the latest snapshot. The table shows how each version's spec text types the field.

Versions	Type in the spec	Required	Deprecated
2.0 to 2.1	array of string	No	No
2.2	array of strings	No	No
2.3 to 2.3.1	string array	No	No
2.4	string array	No	No
2.5 to 2.6-202606	string array	No	No