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Real-Time Bidding APIs

Last updated on April 21, 2017

Real-time bidding in OpenX Ad Exchange is a server-to-server interaction between OpenX ad serving infrastructure and bidders.

Ad Exchange communicates with bidders using one of the following Real-Time Bidding APIs:

Here's how the RTBReal-time bidding, auctioning online inventory within an ad exchange. Buyers bid for the impression based on the value of the user, whereas the seller sets pricing floors and awards the impression to the highest bidder. The auction process takes place in milliseconds, which is why the process is referred to as “real-time.” process works:

  1. Real-time bidder selection. Ad Exchange receives an ad requestCommunication from a web browser or app to an ad server to display an ad. for an available impressionA single display of an ad on a web page, mobile app, or other delivery medium. For deals, impression is a metric to relay the total number of ads that have served. See also billable impression, forecasted impressions. and selects a set of real-time bidders to solicit bids from. Ad Exchange may limit the number of real-time bid solicitations it makes for a single ad request. When there is a surplus of bidders, Ad Exchange chooses those with the best chance of winning the auction.

  2. Bid requestWhen OpenX Ad Exchange receives an ad request, it sends a communication containing details about the impression to selected real-time bidders to solicit bids for it. from Ad Exchange. 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 line items, Ad Exchange includes all of the matching line items in the bid request.

  3. Bid responseAfter evaluating a bid request, a real-time bidder’s communication to OpenX Ad Exchange, indicating if they’re interested in the impression, and if so, how much they’re willing to pay for it.. 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 CPMCost per mille, a pricing method which calculates cost based on the number of impressions (per 1000). bid or a no bid response; that is, 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 line items must provide a CPM bid or no bid response for one of the matching placements so that Ad Exchange can attribute the impression to the appropriate order, line itemThe primary unit of execution for an OpenX order, which represents a specific inventory purchase and the required conditions for ad delivery., and ad. Bidders can include multiple bids in their bid response for a single matching ad.

  4. Auction. After bids are received (or after an allotted amount of time), Ad Exchange executes an auction. Publishers can set a floorThe minimum price a publisher is willing to accept for a given impression. price for their inventoryAd space available on a website or app. The basic unit of inventory for OpenX is an ad unit.; in those cases, any winning bid must be higher than the publisherIn OpenX, an account type that represents a business with ad space to sell.'s floor price.

  5. Ad delivery. 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, this HTML is loaded in the browser. Macros for the winning price and for tracking clicks can be included in the HTML.

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

The following topics describe how to set up your application to process the bid request from Ad Exchange and build your bid response:

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