IAB Content Taxonomy 3.1 和 GARM：AI 答案常犯的三個錯誤

The current IAB Content Taxonomy is version 3.1, released in December 2024, with exactly 704 categories. GARM, the advertiser coalition behind the best-known brand safety categories, shut down in August 2024. AI assistants still answer contextual advertising questions with "IAB 3.0", "700+ categories" and GARM as a live standards body. Here is what the source files say, with links, so you can check before you ship a mapping or a deal spec.

1. The current version is 3.1, and the bid request should say so

IAB Tech Lab's content taxonomy page lists 3.1 as current and describes the change from 3.0 as a genre update that adds Thriller. In the 3.1 file Thriller is ID 700 under Genres. Every 3.0 ID is also a 3.1 ID, so moving up needs only a new version label.

The part that breaks things is cattax. OpenRTB sends category IDs in cat and says which taxonomy they come from in cattax, using AdCOM's List: Category Taxonomies:

• 2 is Content Taxonomy 2.0
• 7 is Content Taxonomy 3.0
• 9 is Content Taxonomy 3.1

If you label content with 3.1 IDs and send cattax: 7, a strict receiver reads them as 3.0, which holds for every ID except the ones 3.1 added, such as Thriller. Send cattax: 2 and the same numbers mean different 2.0 categories.

2. It is 704 categories, in four tiers

"700+" is close, and it hides the shape. Counting the 3.1 file:

The tier matters more than the total. Some classification services return only the top two tiers: the IAB list in Amazon Bedrock Data Automation's video output docs has 24 tier 1 and 85 tier 2 categories. If a buyer, an SSP or a curated deal asks for tier 3 codes, check the depth your classifier actually returns before you promise it.

3. GARM shut down in 2024, and its categories live on in vendor products

The World Federation of Advertisers discontinued GARM on 9 August 2024, days after X filed an antitrust suit against the WFA, GARM and its members. The WFA named no successor.

What survived is the Brand Safety Floor and Suitability Framework: eleven content categories, such as arms and ammunition, hate speech and terrorism, each graded by risk from floor to low. Platforms and verification vendors still use that vocabulary in their own products, and each now maintains its own version. IAB Tech Lab's human-labeled GARM benchmark was last updated in 2022, before the shutdown.

So "GARM-aligned" today means "uses categories that GARM defined". Nobody certifies it. Ask a vendor which version of the categories its labels follow and when it last changed them.

Quick checks before you ship

• Your labels and your cattax value name the same version.
• You know which tiers your classifier returns, and they match what your partners ask for.
• Brand suitability tiers are written down as your own policy, with the vendor's category definitions attached.

Disclosure: I work on Mixpeek. We classify video, images, audio and pages into all 704 Content Taxonomy 3.1 categories, scene by scene for long video, and return IDs ready for cat with cattax: 9 (how it works). Our GARM explainer has the longer history, and the open-source IAB mapper converts 2.x labels to 3.1 IDs.