If you'd like to know more about the Open Bidding feature within Ad Manager, please refer to these articles in the Ad Manager Help Center. For additional information about the Open Bidding product, please use the "?" icon on the top right hand side of your Open Bidding account.

Learn the basics

How Open Bidding works

Life cycle of an Open Bidding request

Open Bidding requests are handled by Ad Manager via a “server-to-server” integration between publishers and their demand partners. Once an ad request is generated, Ad Manager runs a unified auction to determine the best yield. This enables third-party demand partners to compete for your inventory in real-time.

In this article:

About the Open Bidding process

Open bidding process workflow

1. An ad request is triggered and information is passed to the Ad Manager ad server

Requests are sent to Ad Manager using Google Publisher Tags, the Google Mobile Ads SDK, or the IMA SDK. Along with each request, information about the user, device and targeting is passed to Ad Manager. Learn more about the ad selection process in Google Ad Manager.

2. Ad Manager runs a unified auction to determine the best yield

As part of the ad selection process, Ad Manager completes the following steps at the same time:

2a. Ad Manager selects the best trafficked line item to compete in the unified auction

Using targeting and delivery pacing information, Ad Manager catalogs all eligible line items booked in the Ad Manager ad server and selects the best line item to compete via dynamic allocation in the unified auction.

2b. Ad Manager sends a bid request to targeted yield partners

Ad Manager uses yield groups to identify the list of exchanges and networks to compete in the unified auction. Yield groups contain targeting similar to line items and include a combination of Ad Exchange, third-party exchanges and/or Mediation ad networks. For each Open Bidding yield partner assigned to an eligible yield group, Ad Manager sends a bid request to collect their highest bids.

Requests marked as child-directed in compliance with the Children's Online Privacy Protection Act (COPPA) are not sent to Open Bidding yield partners.

2c. Targeted yield partners run their own auction and returns their most competitive bid to Ad Manager

Yield partners utilize their own Open Bidding integration to receive the bid request from Ad Manager, run an auction according to the information provided in the request, and return their most competitive bid to Ad Manager.

2d. Ad Manager hosts a unified auction and selects a winner

Ad Manager hosts a unified auction, comparing yield partner bids, the Ad Exchange bid and other direct line items via dynamic allocation to ensure that each impression maximizes yield.

3. A creative or Mediation list is returned to the publisher

After dynamic allocation and the unified auction has completed, the Ad Manager ad server returns the winning asset to the publisher for display.

  • If an Ad Manager line item wins the unified auction, the Ad Manager creative is returned to the publisher.
  • If an Open Bidding or Authorized Buyers demand partner wins the Ad Manager unified auction, the buyer's creative is returned to the publisher.
  • If a Mediation yield partner wins the Ad Manager unified auction, a Mediation list (or "chain") is returned to the publisher. This list includes Mediation yield partners with a CPM higher than the highest Authorized Buyers or Open Bidding yield partner bid. Ad Exchange always appears at the end of a returned Mediation chain since it's guaranteed to fill the impression. Ad network tags with a lower expected yield than Ad Exchange are excluded from the chain.

    The Google Mobile Ads SDK will then call each yield partner in the list until an ad is returned. If the yield partners are unable to fill the ad request, the request will be unfilled and no automatic passback to the ad server is triggered. Learn more about Mediation for mobile apps

If the default CPM for a Mediation yield partner is defined as higher than the highest bid from an Open Bidding yield partner, the Mediation yield partner will have a first look to fill the impression with no guarantee they will return a bid at the default CPM price.

Ensure that your default CPM values for Mediation yield partners is set realistically to optimize competition.

Understanding auction dynamics

The real-time bids (RTB) from yield partners compete as part of dynamic allocation in a unified auction. The best Ad Manager line item rate, expected Mediation yields and yield partner bids are compared at the same time and the top bid wins the auction. Authorized Buyers and Open Bidding yield partners bid once for each impression.

All participants in the unified auction, including Authorized Buyers and third-party yield partners, compete equally for each impression on a net basis. Participating exchanges run their own auction independently and then submit their bid into the unified auction.

Ad Manager sends the reserve price for the unified auction to all eligible Authorized Buyers and Open Bidding participants (including third-party exchanges or networks). The reserve price is at least the maximum of the temporary CPM calculated by Ad Manager for the best eligible guaranteed line item or the floor price configured by the publisher (as may be adjusted, at the publisher's option, by various Ad Manager optimizations).

The reserve price is not set by either the value CPMs of remnant line items that are competing for the impression or any bids received from any Authorized Buyers or Open Bidders for the impression.

No auction participant receives any information about any other party’s bids prior to completion of the auction.


There are three buyers. Authorized Buyer 1 bids $3.00, Authorized Buyer 2 bids $1.00, and a third-party exchange bids $2.00 on an impression.

The winner of the unified auction would be Authorized Buyer 1, as $3.00 is the highest bid submitted.

The highest net bid (which takes into account Ad Manager’s revenue share) wins. The channel through which a bid is received (for example, whether through Google Ads or Display & Video 360, a third-party Authorized Buyer, Open Bidding yield partner, or a remnant line item) does not otherwise affect the determination of the winning bidder.

Learn more about unified pricing rules and the auction rules.

Open Bidding ad request FAQs

What happens if multiple yield groups are eligible for the same request?

The yield partner lists from each eligible yield group are combined into a single list, so Ad Manager sends each partner only one bid request. If the same yield partner appears in more than one eligible yield group, only one bid request will be sent to the yield partner.

What happens if requested ad sizes don't match the yield group targeting?

In this case, the third-party yield group partners, or "buyers," will be able to bid on whatever sizes overlap between the sizes in the publisher's ad request and the sizes targeted by the yield group. If a separate Ad Exchange line item in Ad Manager targets the sizes that do not match the yield group targeting, Authorized Buyers will still be able to bid on those sizes included in both the publisher's ad request and the Ad Exchange line item.


A publisher's ad request contains three sizes — 300x250, 300x600, 300x50. If a yield group targets only the 300x600 and 300x50 sizes, third-party yield group buyers can only bid for those two sizes, and will not be eligible to submit bids for the 300x250 size.

If a separate Ad Exchange line item targets all three sizes, Authorized Buyers will be able to bid on the 300x250 size in addition to the sizes targeted by the yield group.

Requests with multiple sizes are not supported by Mediation for mobile apps

What information is sent to buyers with each Open Bidding request?

Open Bidding requests are sent to buyers using a modified version of the Ad Exchange real-time bidding protocol buffer or the OpenRTB protocol buffer.

In addition to standard fields from the RTB protocol, exchange bidders also receive the publisher's Ad Manager network code and Ad Manager ad unit code.

How do Ad Exchange or AdSense line items and yield groups compete?

Ad Manager only sends one bid request to Ad Exchange for each unified auction. If both an Ad Exchange line item and a yield group are eligible for the same impression, Ad Manager sends a single request to Ad Exchange. This request follows the code snippet and web property defined in the Ad Exchange line item.

If you use AdSense line items as well, it's good practice not to allow them to overlap in targeting with Ad Exchange line items or non-mediation yield groups.

Competing AdSense or Ad Exchange line items are chosen randomly and are not affected by the delivery yield of historic CPM values under the Dynamic Allocation feature.

In Delivery Inspector, you might see both a yield group and line item listed as "delivered" to an ad slot if the targeting for both an Ad Exchange line item and yield group matched an ad slot.

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