What is OpenRTB?

OpenRTB is a specification maintained by IAB Tech Lab that defines a common format for bid requests and bid responses, so supply-side and demand-side platforms from different companies can trade ad impressions through real-time bidding.

Also known as: Open Real-Time Bidding, OpenRTB protocol

How it works

Real-time bidding only works if many different systems can understand each other in milliseconds. An SSP built by one company needs to describe an impression in a way that a DSP built by another company can read instantly. OpenRTB is the shared format that makes this possible.

The specification defines two main messages:

  • Bid request: sent by the seller side. It describes the impression on offer, such as the site or app, the ad format and size, device details, user signals where permitted and any deals that apply.
  • Bid response: sent back by the buyer. It contains the bid price, the ad or a reference to it, and, if relevant, the deal being bid on.

Inside these messages, information is organised into named objects. For example, OpenRTB 2.6 describes a private marketplace (Pmp) object that holds Deal objects. Each Deal carries a unique id, which is the Deal ID, plus fields such as a minimum bid (bidfloor), allowed buyer seats (wseat) and a guar flag for guaranteed deals. Supply chain transparency information, described in the SupplyChain object, can also travel in the bid request.

Versions

IAB Tech Lab's OpenRTB page lists the 2.x line from 2.0 up to 2.6, and notes that version history is now maintained in GitHub. The 2.6 repository explains that the specification is updated approximately once a month, using dated versions that began with 2.6-202211. OpenRTB 3.0 was released in September 2017 alongside a companion specification, the Advertising Common Object Model (AdCOM). According to the standards page, 2.6 also uses AdCOM 1.0 lists for faster updates. When working with a partner, it is worth confirming which version and which optional fields they support, because platforms adopt changes at different speeds.

Why it matters

IAB Tech Lab's standards page calls the OpenRTB specification "the foundation of the programmatic advertising ecosystem." Without a shared protocol, every SSP and DSP would need a custom integration with every other, which would slow trading and limit competition.

For publishers and media owners, OpenRTB support shapes what information buyers receive. If a seller's systems pass clear, accurate signals about format, placement, content and deals, buyers can value the inventory properly. If signals are missing or wrong, bids tend to be lower or absent.

Example

Illustrative example. A mobile game developer's SSP sends an OpenRTB bid request for a rewarded video placement. The request names the app, the video format and duration, the device type and a Deal ID for a private marketplace with a toy brand's agency. The agency's DSP reads the request, recognises the Deal ID and returns a bid response with a price above the deal floor and a reference to its video creative.

IncrementX perspective

OpenRTB is part of the plumbing that connects represented inventory to programmatic buyers. When IncrementX connects inventory with DSPs, trading desks and programmatic buyers through the Demand Marketplace, deals such as PMP, PG and curated packages reach buyers as Deal IDs inside this kind of bid request. Clear, well-structured inventory information is part of good representation, because it is what buyers' systems actually see.