Deciphering Ad Tech

Unraveling the Differences Between Header Bidding and RTB

The digital advertising landscape has undergone significant transformations, with header bidding emerging as a revolutionary approach, highly regarded by advertisers and publishers. Its appeal lies in the promise of higher publisher yields and a more competitive structure for advertisers, positioning it as a pivotal development in ad tech.


Previously, Real-Time Bidding (RTB) held the title of being the transformative force in programmatic advertising. Its introduction brought about automation, the ability to leverage extensive user data, and the capability to operate in real-time, making RTB a solution to the complex and often cumbersome traditional ad-buying processes.


Despite their similarities in rapid ad buys, data-driven decision-making, and automation, header bidding has gradually outpaced RTB. 


The question arises: what distinguishes the two, and why has header bidding become the preferred choice?

Evolving Solutions in Digital Advertising

To understand the distinction between RTB and header bidding, it’s essential to view them as solutions to the limitations of their predecessors. 

RTB was designed to overcome the challenges of traditional manual ad-buying, while header bidding emerged to address the shortcomings inherent in programmatic strategies, including RTB.

Challenges with RTB​

Real-time bidding operates by auctioning impressions in the moments before a webpage load, using automation to facilitate rapid bidding. Bidders receive data about the available impression and the associated user, with the winning bidder paying slightly more than the second-highest bid. RTB marked a significant improvement over manual ad buys by allowing individualized auctioning of impressions and refined audience targeting. However, RTB soon faced its challenges, including the inefficiency of waterfall processes, variations in RTB types causing disparities in access, and the prioritization of Google’s AdX exchange in Google DFP.


The Waterfall Dilemma and Inefficiencies

In RTB, publishers used a waterfall approach by sequentially auctioning ad inventory through different ad exchanges and SSPs. This often left advertisers with only “leftover” inventory, leading to perceptions of subpar choices and a lack of pricing transparency.


Variations in RTB Access

RTB isn’t a monolith; it encompasses various programmatic transactions, including “open auctions”, “preferred deals”, and “private auctions”. These exclusive transactions often precede open auctions, allowing participants early access to premium inventory.


Google's DFP and AdX Exchange Prioritization

Google DFP’s prioritization of its AdX exchange in publishers’ waterfalls disadvantaged other exchanges and advertisers, disrupting the overall fairness and effectiveness of the system.

The Emergence of Header Bidding

Header bidding addresses these RTB challenges by implementing a unified auction system in a web page’s header. This method enables simultaneous competition among multiple SSPs and ad exchanges in a single auction, bypassing the waterfall approach. Crucial data is sent to bidders, and the winning bid competes with direct deals on the publisher’s ad server.

Distinguishing Header Bidding from RTB

Header bidding offers several improvements over RTB:

  • Unified auctions replace successive auction calls, increasing efficiency.
  • Access to premium inventory is democratized, enhancing advertiser opportunities.
  • Open-source infrastructure counters proprietary platform manipulation.

The Future of Digital Advertising

While header bidding is currently the preferred digital advertising system, it is challenging. As the industry continues to evolve, new solutions will likely emerge to address the limitations of header bidding, further advancing the field of digital advertising.

** This article, by Ronen Cohen, SelectMedia’s CTO, presents the most up-to-date comparison of Header Bidding versus RTB as of early 2024. It offers a comprehensive understanding of these pivotal technologies in the evolving digital advertising landscape.

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