Tags: Optimisation tips

Updated: February 20, 2023

Header bidding is a programmatic ad sales technique, which is used by more than 70% of publishers to e.g. boost eCPMs, increase fill rates, and maximize ad revenues. Header bidding can be implemented in two different ways, either as a so-called client-side or a server-side implementation.

In a server-side implementation a single call is made from the web page or application to a server, which then continues making calls server-side to all integrated demand sources. The "wrapper" sends all bids and prices back to the publisher, so pricing is transparent. This is different compared to a client-side call, where all calls are being made from the user's browser, which in most cases takes slightly longer.

Server-side is a particularly functional solution on mobile where high bandwidth is necessary to sustain the connection and ensure the ads are properly delivered. In order to maintain good site speed, there is a limit of how many bidders you can run client-side as each one adds a bit of latency to the setup. With server-side setups such limitation does not exist as the auction is held on a separate server, which enables you to have a larger number of demand partners running without a negative impact.

Publishers' interest in server-side header bidding has clearly been growing recently. A server-side implementation can be a good solution if you want to improve your site experience, technical manageability, or efficiency, but it is also more complicated to implement.


What does it mean for a development team working with server-side?

Server-side requires a different setup compared to client-side, as the auction takes place on a server, rather than in the user’s browser. So the publisher chooses a server-side bidding technology partner to implement and host the solution; or they build this server structure themselves - often using the Prebid Framework.

The publisher's development team must therefore implement a prebid-server in order to be able to compete for demand sources on the server. Additionally, you need to find an easy way to change the server-side implementation code if necessary, as well as a way to monitor the performance of the implementation. The Prebid Framework is also constantly evolving, which means that the implementation must also be updated and kept up to date.

If the publisher has built their own implementation, the maintenance tasks already take up considerable technical resources. It is often more sensible to turn to technical partners (such as Relevant Digital) to reduce the technical burden of server-side implementation.

Working with a partner is also usually a cheaper option than building and maintaining a complex technical implementation yourself. This will ensure that your development team's resources are saved for doing the core business - which in most cases makes the most sense.


With Relevant Yield HB Manager you enable quick tests and changes without having to worry about maintenance work

Several ad tech providers have developed their own wrappers for client-side header bidding, and some of them also support server-side header bidding.

The Relevant Yield solution can do both. Furthermore, you can select if you want to do a client-side call, a server-side call - or both in parallel. It might seem counterintuitive to call both client- and server-side with the same call, but different SSPs are focusing bid strategies on different call types, and some are just stronger in one call type, than the other; so it is certainly a good idea to test the performance. 

If advertising is not distributed in the browser but in the application, server-side is a natural choice. Relevant Yield wrapper, HB Manager, supports server-side, working with the prebid framework, and supports all of the server-side components in the framework: Prebid Server, Prebid Mobile, Prebid AMP, Prebid Video. Where the latter three are extensions on the core Prebid server.

The HB Manager enables flexible testing and experimenting with different options; you can easily change the configuration from the UI to select whether a bidder should run client-side or server-side. This allows you to find the optimal setup for you; how many bidders should I run client-side vs server-side? What impact does it have on page speed if I decrease the number of client-side bidders and does it generate a desired uplift in KPIs?

HB Manager is also a great tool for testing new partners, as the auction takes place in a secure and controlled environment and the adapter can be quickly turned on and off without affecting the user experience.

The benefits of a server-side implementation hosted through HB Manager for a publisher include:

  • You do not need to build or host the Prebid Server.
  • A solution for latency issues - faster loading of ads.
  • Speeding up technical implementation can affect the viewability of ad placements and thus the appeal of your inventory to advertisers.
  • It works better for Rich Media: videos are often slow to load, so switching to server-side bidding greatly improves user experience. A server-side implementation is also the only way to show ads on over-the-top (OTT) devices.
  • You do not need to add a monitoring or analytics system for your Prebid server.
  • Unified header bidder reporting through our HB Analytics solution, which covers both client-side and server-side header bidder reporting.
  • Easy setup: identical setup to the client-side and no extra mapping; just activate with a single click if you want to run the same settings as on the client-side. You can also differentiate your demand sources based on the call type you utilize, making sure you work with the best sources in each individual case and mediatype.
  • Switch between methods at a click of a button, or even run in parallel. You can mix load types on a placement level to utilize the perfect call structure on each individual level.


If you wish, you can find out more about HB Manager here or if you have any questions or would like to find out more about the solution book a meeting here.

Relevant Yield in 2mins


Suvi Leino
By: Suvi Leino

Responsible for marketing and communications at Relevant Digital.