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Working with Multi-size Bid Requests

Demand Partners

Last updated on January 16, 2019

OpenX allows its publishers to support creatives for multiple ad sizes on a single impression opportunity and sends a single bid request for each ad size. You can can choose to consolidate those ad sizes in to a single request using the format object.

To be able to return bids for multiple sizes in a single impression opportunity:

  • Make sure your bidding application logic can ingest all the sizes transmitted in the array of the format object in OpenRTB 2.4.
  • Ask your Platform Development Manager to enable format object support for your account.

The format object array includes widths and heights, so you must include bid.w and bid.h values in the bid response. For example, a bid request includes a banner populated with a format object that indicates availability of a 728x90, 320x50, and 160x60 creative:

"banner": {
            "format": [
                {"w": 728, "h": 90},
                {"w": 320, "h": 50},
                {"w": 160, "h": 60}


You can submit a bid for any one of the ad sizes, or a multi-bid for several sizes.