AdCOM (Advertising Common Object Model)

AdCOM (Advertising Common Objects Model) is an IAB Tech Lab specification that works in tandem with the core foundational OpenRTB specification. It was developed to reduce fragmentation across the programmatic ecosystem by creating a consistent, extensible vocabulary that Programmatic Supply Chain constituents can rely on when describing programmatic inventory.

The Advertising Common Object Model or AdCOM specification has two parts: the first leverages the Object Model to support OpenRTB 3.0, which was not widely adopted by the ecosystem. The second is enumerated lists that pertain to specific attributes in OpenRTB 2.x. It has ubiquitous adoption because it provides modularity by enumerating common values pertaining to given attributes. Thereby making bid requests smaller while providing more accurate atomic descriptions of a piece of inventory. For example, describing an instream video execution, the video.plcmt attribute without AdCOM would result in a bid request reading video.plcmt=instream; with AdCOM the same request reads video.plcmt=1. While that may not seem like a big change, small savings like that add up a lot across multiple attributes and billions of requests per second.

OpenRTB remains the transport and auction protocol; AdCOM supplies a set selection of specifically enumerated values that OpenRTB references in a bid request. When a bid request is generated, supply-side platforms include AdCOM-aligned descriptors of the placement and its constraints. Bidders get an easily readable, static list they can use to evaluate the inventory. The practical benefits are fewer integration errors, and smaller bid requests — because everyone shares a single, extensible model. For organizations already using OpenRTB, adopting AdCOM means clearer contract surface area when evaluating inventory, reduced bespoke mapping logic, and a smoother path for introducing new ad experiences across the ecosystem.