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A Beginner’s Guide to Server Side Header Bidding

Server Side Header Bidding
Server-side header bidding has all the buzz these days and rightfully so. More and more publishers are choosing to run it on their sites and see a huge impact in revenue increases. If you’re not sure what server-side header bidding is, this post will take you through its basic elements, pros, cons, and more.

In just a few years, header bidding grew from being virtually unknown to an industry-standard technique, with nearly 67.7% of the US publishers leveraging header bidding to monetize their inventories in Q3 2021 (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 will be. So, to deal with the pitfalls such as latency and improve the user experience, Server-to-server header bidding was introduced. Here’s everything you need to know about why publishers are switching to the server to server header bidding, how it works, and more.

Table of Contents

What is Server-to-Server Header Bidding?

Server-to-server header bidding (also known as server-side header bidding or S2S header bidding) is a programmatic technique wherein the auction takes place on the ad server instead of the user’s browser. It enables your website to simultaneously work with multiple demand partners without compromising on 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. Here’s a step-by-step explanation:

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 i.e. Google Ad Manager.
  • This winning bidder will then compete with the publisher’s Guaranteed deals and Google Ad Exchange in the ad server.
  • The ad server selects the highest bidder and the ad is served to the users.

Server Side Header Bidding Workflow

Benefits of Server-side Header Bidding

As we discussed above, Server-side header bidding is a great solution to the limitation of traditional header bidding. It can be useful when you have a high volume of impressions and a higher number of demand sources that need to compete for each impression. Let’s take a quick look at what Server-side header bidding can do for you.

  • Reduced latency: 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 factor 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. Serving video ads 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 during a session. Whereas Server-to-server header bidding remains unaffected from such problems since it doesn’t depend on the browser to send ad requests.

Benefits of Server Side Header Bidding

3 Vital Things to Know 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 a 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 to a Server-side set-up, they lose access to the user and can’t drop cookies. As the SSPs or ad exchanges have to identify each user in order to deliver targeted ads, they need to sync their cookie. However, this no longer works in server-side header bidding and results in lower eCPMs for the ad impressions.

How to Choose The Right Server-to-server Header bidding Provider?

The 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 a server-side header bidding vendor, consider these: the type of inventory on your website, current demand, and upcoming advertising trends. Here are a few more factors 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, the gap created between the user and the wrapper 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 capability to identify users. 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 match 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. Here’s a list of header bidding analytics providers that you should check out.

Is Open Bidding a Server-side Header Bidding solution?


Open Bidding is Google’s server-side header bidding solution that allows publishers to sell ad impressions available via Google’s Ad Exchange and other SSPs/Ad Exchanges in real-time. In case you’re interested in a deep dive, we’ve written a detailed guide on everything you should know about Open Bidding

The future of server-side header bidding

As the debate of client-side vs. server-side header bidding slowly settled down in the last couple of years, a fundamental question has started picking up lately: what will happen to client-side header bidding when cookies become obsolete? Will server-side gain popularity amongst publishers?

The answer to this question varies from publisher to publisher. There will be some publishers that will shift to server-side header bidding as it promises higher-yielding competition and reduced latency. Nonetheless, more publishers will still prefer client-side header bidding because of better transparency and fair auction dynamics. Besides, publishers will have an option of running both – client-side and server-side auctions and it is likely to be adopted in the future. 

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, the best way forward for the publisher is to deploy a combination or hybrid header bidding.

Need any help with the implementation? We’re offering a ‘7-day free consultation’ to a limited number of publishers. Not only will we audit your website, but we’ll also provide you with actionable recommendations to improve your eCPM and overall ad revenue. 

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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