AdCOM

AdCOM (Advertising Common Object Model) is the IAB Tech Lab specification that defines the shared objects and code lists used by its trading protocols, such as ads, placements, users, devices, sites and apps.

The IAB Tech Lab organises its OpenMedia specifications in four layers. Layer 1 moves bytes, layer 2 sets their format, layer 3 defines a transaction, and layer 4 describes the things being traded. AdCOM is layer 4. OpenRTB 3.0 uses AdCOM 1.0 as its domain layer, and OpenDirect 2.1 adopted AdCOM objects too (IAB Tech Lab, AdCOM 1.0).

Most engineers meet AdCOM through OpenRTB 2.6, which dropped its own enumerated lists and points to the AdCOM lists instead. Those lists give meaning to the integers in a bid request: device types, API frameworks, category taxonomies, creative attributes and ID match methods. AdCOM calls itself a living specification, so new list values can appear without a version change, and implementers must accept them without breaking.

Example: A bid request with "devicetype": 3 describes a connected TV, and "cattax": 9 says the content categories use IAB Tech Lab Content Taxonomy 3.1. A DSP that hard-coded an old list would misread both, which is why parsers should load the current AdCOM lists.

Related terms: OpenRTB, OpenDirect, CTV, contextual targeting, OM SDK, bid request.

Authoritative source: IAB Tech Lab, "AdCOM Specification v1.0" (GitHub, accessed 9 November 2026).

Read the full guide: OpenRTB 2.5 vs 2.6 vs 3.0: what changed and what is used.