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Demand Partners

OpenX supports real-time bidding via IAB’s OpenRTB 2.5 specification.

You can use the OpenRTB structure and its enumerated values to write applications that bid on ad space in OpenX Ad Exchange and other compatible exchanges and supply sources. Bidders that are already compatible with these versions should be able start using the OpenX OpenRTB implementation with minimal custom integration work.

When participating ad inventory becomes available, OpenX sends JSON data in an OpenRTB BidRequest to describe the ad inventory, the user, and other details. Demand Partners can send an OpenRTB BidResponse in JSON format and set up optional win notifications and loss notifications.

OpenX provides its publishers with an OpenRTB ad call parameter to send additional data to buyers in each BidRequest. For details, see supplemental data enrichment.

The diagram below provides a graphical overview of the process described above:

How Real-time Bidding Works

Real-time bidding (RTB) in OpenX Ad Exchange is a server-to-server interaction between the OpenX ad serving infrastructure and bidders. OpenX Ad Exchange communicates with bidders using the OpenRTB (JSON) Real-Time Bidding API.

OpenX supports real-time bidding via the IAB’s OpenRTB 2.5 specification.

Here’s how the RTB process works:

  1. Real-time bidder selection. OpenX Ad Exchange receives an ad request for an available impression and selects a set of DSPs from whom to solicit bids based on individual DSP inventory targeting settings and their QPS allocations.

  2. Bid request from OpenX Ad Exchange. OpenX Ad Exchange passes a bid request with details about the specific impression to the selected real-time bidders and solicits bids for it. The bid request may contain optional targeting information. If a single bidder has multiple matching traffic sets, OpenX Ad Exchange includes all of the matching traffic sets in the bid request.

  3. Bid response. Each bidder receives the request, evaluates the bidding opportunity, and responds with a bid response (even if the bidder does not want to place a bid).


    The response contains either a CPM bid or a “no bid” response. Bidders must respond to bid requests because timeouts have a negative impact on the number of bid requests sent to the bidder.

    Bidders with multiple matching traffic sets must provide a CPM bid or a “no bid” response for one of the matching placements so that OpenX Ad Exchange can attribute the impression to the appropriate business unit, traffic set, and ad. Bidders can include multiple bids in their bid response for a single matching ad.

  4. Auction. After OpenX Ad Exchange receives bids (or after an allotted amount of time), it executes an auction. Publishers can set a floor price for their inventory. In those cases, any winning bid must be higher than the publisher's floor price.

  5. Ad delivery. OpenX Ad Exchange delivers the ad of the winning bidder. The BidResponse contains the HTML for the ad the bidder wants to serve. When the bidder wins the auction, the viewer’s browser or app loads this HTML.


    Macros for tracking clicks must be included in the HTML. Additional macros, like price macros, can also be included.

  6. Result notifications. OpenX Ad Exchange sends result notifications, in the form of an auction results message, for each bid it received for a given auction.