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A Beginner’s Guide to Server Side Header Bidding

Server Side Header Bidding
Header Bidding has always been a focus for the publishers to increase their eCPM, And Server Side header bidding is one of the methods that most publishers are adopting now. So, Let's learn what is it & how it works.

In just a few years, header bidding grew from being virtually unknown to an industry-standard technique, with nearly 67.8% of the US publishers leveraging header bidding to monetize their inventories in December 2020 (Src).

Although client-side header bidding has been the most preferred method for header bidding, server-to-server header bidding is gradually gaining traction among the publishers. 


Because in client-side header bidding, the more the number of demand partners added to the auction, the slower the page load will be. So, to deal with the pitfalls such as latency and improve the user experience, server-to-server header bidding was introduced.

“Header bidding is great, but it may not be a cure-all. Server-to-server is the next step in the evolution of auction dynamics.”

– Chip Schenck, VP of programmatic sales and strategy at Meredith

Although moving to server-to-server or Server Side Header Bidding is not exactly a big leap, it’s still an important step you can take to remove the latency issues that occur with client-side header bidding. 

Table of Contents

What is Server-to-Server Header Bidding?

Server-to-server header bidding or server side header bidding or S2S header bidding is a programmatic technique wherein the auction takes place on the server instead of the user’s browser. It enables your site to simultaneously work with multiple demand partners without compromising on the page speed.

Let’s dwell more on it in the coming sections.

How Does Server-to-Server Header Bidding Work?

Server-to-server header bidding works essentially the same way as client-side header bidding, the only difference is that less implementation work is required. That being said, you still have to put some JavaScript code in your header to send an ad request to your demand partner. 

Step-by-step explanation:

  • When a user visits a website, the JavaScript code located in between the head tag executes and sends a request to the server-to-server vendor.
  • The server will then send out bids to multiple demand sources.
  • Among them, whichever is the highest bidder will win and the winning price is passed to the publisher’s ad server.
  • This winning bidder will then compete with the publisher’s Guaranteed deals and Google Ad Exchange in the ad server (GAM).
  • The ad server selects the highest bidder and the ad is served (i.e. displayed on the page).

Server Side Header Bidding Workflow

3 Vital Things About Server-to-Server Header Bidding

Server-to-server Header Bidding is easier and faster

In client-side header bidding, browsers send and receive information through a limited amount of browser ports. So, if a publisher calls for more partners than the available ports, there’s a possibility for some partners to not be selected, potentially denying publishers access to the best bids. Server-to-server, on the other hand, isn’t constrained by a small number of ports, making it possible to call multiple partners simultaneously. More bids mean higher yield for publishers.

Server-to-server header bidding requires a transparent partner.

In server-to-server bidding, publishers work with just one vendor and that vendor collects up bids from all the other demand partners. And that’s why a trustworthy partner is important to run the auctions fairly.

Cookie matching via server-to-server header bidding is complex.

When the SSPs move from a client-side setup to a server-to-server, they lose access to the user and can’t drop cookies. As the SSPs or ad exchanges have to identify each user, they need to sync their cookie.

In this case, they do it on the server-to-server. But not all cookies match up and unsynced users might get extremely low bids or no bid at all, so the impact is significant. However, with the expected removal of third-party cookies from Chrome, it might not be a big disadvantage in the future.

Choosing Server-to-Server Over Client-side Header Bidding

Let us check how advantageous server-to-server is over client-side Header Bidding:

  • Reduced latency: As mentioned, server-to-server header bidding is carried out in a server instead of a browser, this reduces the overall page load time. Although it varies just by a few milliseconds when compared with client-side header bidding, publishers still take page latency as an important element as it affects the overall user experience.
  • Access as many demand partners: With server-to-server header bidding, you can send bid requests to as many buyers as you want. This increases competition and offers a better ad fill rate.
  • Perfect for video header bidding: Videos take more time to load on web pages than any other ad format. Using video with the client-side can damage the user experience. However, with server-to-server header bidding, such complications won’t occur and video header bidding will work perfectly.
  • No browser request limitation: Since web browsers have a limit to the number of requests they can generate, publishers that use Client-side Header Bidding can only send a few ad requests via a browser during a session. While server-to-server Header Bidding remains unaffected from such problems as it doesn’t depend on the browser to send ad requests.

Benefits of Server Side Header Bidding

Choose The Right Server-to-Server Header bidding Provider

The best way forward to know which solution provider fits best with your monetization strategy is by selecting and testing the solution they offer and seeing how it impacts your revenue in the long run. While choosing, consider these: the type of inventory on your website, current demand, and upcoming advertising trends.

Here are a few entities that you need to be aware of before choosing the provider:

User Experience

How will the solution offered by the chosen provider impact your user experience? There are two elements that not just negatively impact your latency but also impact your user experience — the time it takes to initiate an ad request and the time taken by different demand partners to return the final bidding price to the ad server.

As the core functions of the wrapper move away from the user’s browser to the server, a gap is created between the user and the wrapper, and this can add latency to your page. So, check the impact of latency and look for a partner that can help you mitigate it.

Overall Revenue

This is the most important entity for publishers to look into. There are two key factors to consider when examining your revenue — incremental demand and cookie syncing. A more impactful server-to-server is the one that can add premium incremental demand without negatively impacting latency and also offers an increased user sync rate because any decrease in it can have a negative impact on your revenue.

Transparency and Fairness

It’s well known that transparency is key for creating a fair auction that ensures impressions go to the highest bidder and no dollars are shifted from publishers’ pockets to middlemen buried in the supply chain. So, check if there are any added charges to the provider’s server-to-server offering. 

Along with these questions, also ensure that the server-to-server provider you choose offers you clear auction dynamics, testing capabilities, and services to take on the heavy lifting of implementation and upgrades.

Besides, it’s not that easy to evaluate demand partners. For that, you should employ an analytics vendor that provides the market-best analytic solution for monitoring and optimizing server-to-server header bidding setups and thus, better evaluate demand partners. The richer the analytics, the better the publisher can optimize monetization.

What’s Next?

No matter which header bidding wrapper solution you choose, what’s important is that you should get fair and market-determined eCPM for your impressions. Of course, both (server-to-server and client-side) wrapper solutions have their advantages and disadvantages, so the best way forward for the publisher is to deploy a combination or hybrid header bidding. Need any help with the implementation, reach out to us. 

Automatad Team

At Automatad, we help publishers to monetize better without hampering the user experience. Our products are live across hundreds of publishers, earning them incremental ad revenue with every passing second. You can request a free audit to get an estimated revenue uplift today.

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