Client-Side vs Server-Side Header Bidding | What’s Better?

Header bidding revolutionized programmatic advertising by creating a level playing field for all demand partners.

In this article, we will survey the two types of header bidding – client-side and server-side – and determine which is best for publishers.

What Is Header Bidding?

Header bidding is an advanced programmatic advertising technique that enables multiple advertisers to bid simultaneously on your ad inventory even before the webpage is loaded.

In doing so, header bidding increases competition among advertisers, which results in higher revenue for publishers

What Is Client-Side Header Bidding?

Client-side header bidding, as the name suggests, happens on the client-side, i.e., on the user’s browser.

When a user loads a web page, the ad server sends a request to multiple ad exchanges or demand-side platforms (DSPs) simultaneously.

The ad exchanges respond with their bids, and the highest bidder wins. The winning bid is then sent back to the ad server, and the ad is displayed on the page.

What Is Server-Side Header Bidding?

Server-side header bidding happens on the server-side. When a user loads a web page, the ad server sends a request to a server-side header bidding partner, which then sends the request to multiple ad exchanges or DSPs.

The ad exchanges respond with their bids, and the highest bidder wins.

The winning bid is then sent back to the server-side header bidding partner, who then sends the ad to the ad server, and the ad is displayed on the page.

Client-Side Header Bidding: Advantages

client side header bidding pros and cons


Client-side bidding enables cookie matching, where advertisers can access browser cookies to run personalized ads. This can lead to higher CPMs, as users are more likely to engage with ads that are relevant to them.


Another benefit of client-side bidding is transparency.

Since all calls are made directly from the user’s browser, it’s easier to track where bids are coming from and how auctions are being conducted.

This can be beneficial for both publishers and advertisers, as it allows them to see where their money is going and make more informed decisions.


Since the process takes place on the user’s browser, publishers have more control over demand partners and can tweak the code as needed.

However, this does require a skilled professional with programming knowledge to manage effectively.

Client-Side Header Bidding: Disadvantages

Slower Loading Times

As the entire process takes place on the user’s web browser, there can be increased latency which can negatively impact user experience and result in decreased traffic.

This can be especially problematic for pages with video ad units that require a large amount of processing power.

Few Numbers of Bids

Another disadvantage of client-side header bidding is the limit on the number of bids made in the auction.

Browsers are limited in the number of network connections they can establish, which can result in fewer bids being made.

Browser Compatibility

Not all browsers are created equal, and if the user’s browser is not up-to-date or compatible with the code, it can lead to a decrease in ad revenue.

Server-Side Header Bidding: Advantages

server side header bidding pros and cons

Faster Page Load

One of the main benefits of server-side header bidding is faster page load times. Since all calls are made on an external server, the process does not slow down the page loading time for users.

This is particularly advantageous for video ad units and can improve the user experience and increase page traffic.

More Bids

By moving the auction process to a server, there is an unlimited number of SSPs, ad exchanges, and ad networks that can participate in the auction, which leads to increased competition.

Easier to Implement

Since the inventory is hosted on a server, there is no need to make changes to the website’s code, which can be complex and time-consuming.

This can be especially beneficial for publishers who do not have a programming background and want to avoid potential technical difficulties.

Server-Side Header Bidding: Disadvantages

Difficult to Customize Ads

Without access to browser cookies, advertisers may struggle to identify users, leading to lower CPMs.

Lack of Transparency

When the auction process occurs on an external server, publishers may have limited access to bidding data, which can make it harder to optimize their inventory and make informed decisions.

Hosting Costs

Hosting a server for server-side header bidding requires an additional cost. This is an important factor to consider for publishers who want to adopt this method but have limited resources.

What’s the Best Method: Client-Side or Server-Side?

The answer is… both!

Our monetization experts developed a proprietary hybrid header bidding solution that combines the advantages of both methods, while discarding the disadvantages.

This innovative solution involves real-time decision-making on how to distribute requests and initiate parallel auctions on both methods.

By doing so, publishers can take advantage of the high CPMs of client-side header bidding while also benefiting from the speed and fill rates of server-side header bidding.

This technology allows publishers to optimize their revenue streams by leveraging the best of both worlds. In fact, hybrid header bidding has been shown to outperform standard header bidding by an average of 18%.

To learn more and see how you can get started, please contact us today.

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