TechLand Blog

Post-Bid: A technologically convenient auction in the Programmatic Ecosystem

The programmatic ecosystem consistently experiences fresh updates as far as the advertising bids are concerned. To combat the inefficiencies arising from the traditional waterfall method, header bidding (link to the header bidding article) came into the limelight; opening a plethora of opportunities for multiple demand partners to get access to a publisher’s premium inventory. 

But did you know that page latency is a major drawback in the header bidding technique? If you are using a header bidding provider or are extensively investing in technological resources, this issue can be rectified to some extent. However, if either of these is not your option, then, in that case, post-bidding is your best bet. 

What is post-bid?

Post bidding is a technique through which a publisher’s demand sources compete in an auction after the publisher’s ad server rejects a direct-sold or an exchange-based line item. After the ad server calls the post-bid line item, the demand partners from different SSP’s are invited to compete in simultaneous auctions; with the winning partner’s ad eventually being delivered to the user. Let us understand how the entire process works.

No alt text provided for this image
  1. When a website page is loaded, it calls the ad server (GAM, for example) of the publisher’s website. 
  2. The ad server then examines the line items to sell the impression to the different demand partners through a unified auction. The line item consists of a choice between direct-sold, exchange-based and post-bid line items. 
  3. If the post-bid line item is selected by the ad server, it triggers a header auction.
  4. The demand partner with the highest bid wins the auction. This advertiser’s ad is then rendered to the user.

 Advantages of the post-bid technique

  1. Less complexity: Post bidding requires fewer resources and engineering assistance as far as implementation is concerned. A third-party tag, known as the prebid.js tag, is all that requires to be served to the page. Once done, it shall automatically run an auction across all demand sources every time a post-bid line item is selected by the ad server. 
  2. Reduces latency: Latency is the delay between a user’s action and a web browser’s response to that action. In post bidding, the ad server receives the impression as soon as the page loads. The auction starts as soon as the ad server receives the creative which, in turn, reduces the latency. 

Drawbacks of the post-bid technique

a) Low rate of increase in revenue: While header bidding can uplift your revenue by almost 50%, it is not the same with post bidding. 

This is because of the dual auction that takes place in header bidding. As a result, you get a real-time price from multiple demand sources from various SSP’s followed by another round of action between the demand partner with the highest bid and the direct line items. However, in post bidding, the ad server picks the post-bid line item based on a historical price against a real-time price. 

b) Browser overloading due to multiple post bid auctions: In case your page has more than one ad unit loaded, the prebid.js tag needs to be added to every ad unit. In case, a post-bid line item is chosen by the ad server for both the ad units, it may overload your browser due to multiple auctions happening simultaneously. 

c) Lack of specifics while reporting: Ad servers usually provide an aggregated report on post-bid data. There is no specific data available about which demand partner wins how much inventory. The publisher must depend on a third-party analytics provider to get access to reports of the individual demand partners. 

Now the question arises that if auction between demand partners is common in both the techniques, how is header bidding different from post bidding? 

No alt text provided for this image

Post Bidding v/s Header Bidding

In post bidding, the ad server first receives the impression as soon as the page is loaded. After having selected the post-bid line item, the auction between the demand partners is triggered. Eventually, the ad of the advertiser, who wins this auction, will be served to the user without any secondary auction. 

On the contrary, in header bidding, when the page is loaded, the auction between various SSP’s is immediately triggered. The winning bid then competes with the direct-sold line item in a secondary auction. The highest bidding demand partner from the secondary auction is then connected to the user by the publisher’s ad server. This is where the latency drawback comes into the picture. 

Given the pros and cons, it’s about the amount of technological investment a publisher is willing to undertake that directs the choice of the bidding technique. 


Leave a Reply

Your email address will not be published. Required fields are marked *