Key Takeaways

• Prebid Server moves header bidding auctions from browsers to servers, reducing page latency

• Server-side header bidding allows for more bidders without impacting user experience

• Implementation requires technical expertise but offers scaling advantages for publishers

• Cookie matching challenges can impact targeting accuracy and potentially lower CPMs

• Growing adoption makes it increasingly important for mid-to-large publishers

What is Prebid Server, Anyway?

If you've been around ad tech for a minute, you're familiar with header bidding. It revolutionized how publishers monetize by letting multiple demand sources compete simultaneously before the ad server call. But traditional client-side header bidding has its limts — browser overload, latency issues, and caps on bidder numbers.

Enter Prebid Server.

Prebid Server is an open-source solution that moves the header bidding auction from the user's browser to a remote server. It's esentially header bidding without the "header" part, since the auction happens server-to-server rather than directly in the user's browser.

How Does Prebid Server Actually Work?

The workflow is pretty straightforward:

1. When a user visits a webpage, a single request gets sent to the Prebid Server

2. The server distributes bid requests to multiple demand partners

3. Demand partners send their bids back to the Prebid Server

4. Prebid Server aggregates all bids and determines winners

5. The winning bid info is sent back to the publisher's page

6. The publisher's ad server makes the final decision on which ad to display

This server-side approach solves several issues that plague client-side header bidding implementations.

Server-Side vs. Client-Side Header Bidding

Let's compare the two approaches:

The Big Benefits of Prebid Server:

1. Improved Page Performance

Moving bidding logic off the browser reduces the JavaScript burden on users' devices. According to a study by Pubstack, server-side implementations can improve page load times by 20-30% compared to heavy client-side setups.

2. Scale Without Sacrifice

With client-side header bidding, adding more bidders means more browser resources. Prebid Server lets you scale up demand partners without impacting user experience. Some publishers work with 20+ bidders through server-side implementations.

3. Better for Mobile and AMP

Server-side header bidding works particularly well for mobile apps and Google AMP pages, where client-side header bidding is either problematic or not supported.

4. Unified Auctions

Prebid Server can combine both client-side and server-side auctions, giving you consolidated reporting across all demand sources.

The Not-So-Great Parts

Nothing's perfect, and Prebid Server has some drawbacks:

1. Cookie Matching Challenges

The biggest issue is user identification. When bidding happens server-side, cookie matching becomes more difficult. According to ConnectAd, this can result in 10-20% lower match rates compared to client-side bidding.

2. Complex Implementation

Setting up Prebid Server requires more technical resources. You'll need:

• Application servers

• Database servers

• Load balancers

• Caching infrastructure

3. Potentially Lower CPMs

Those cookie matching issues? They can translate to less precise targeting and ultimately lower CPMs for some inventory types, particularly when targeting is critical to the campaign.

Implementation Options

You have two main paths for implementing Prebid Server:

1. Self-Hosted: Run your own Prebid Server infrastructure. This gives maximum control but requires significant technical resources.

2. Hosted Solution: Use a provider that offers Prebid Server as a service. Companies like Magnite, PubMatic, and Index Exchange offer managed Prebid Server solutions.

For most publishers, the hosted route makes more sense unless you have specialized needs or a large engineering team.

When Should You Consider Moving to Prebid Server?

Server-side header bidding makes the most sense if:

• You're working with 10+ demand partners

• Page performance is suffering due to client-side header bidding

• You have mobile apps or AMP inventory

• You have the technical resources to manage the implementation

Smaller publishers with just a few demand partners might not see enough benefit to justify the switch.

What's New in Prebid Server for 2024?

The Prebid Server ecosystem continues to evolve. Recent developments include:

• Improved user ID solutions to address cookie matching challenges

• Better support for video and CTV inventory

• Enhanced analytics and reporting tools

• More sophisticated auction algorithms

According to recent discussions on Reddit, many publishers are now implementing hybrid approaches, running some bidders server-side and others client-side to optimize for both performance and match rates.

Wrapping Up

Prebid Server represents an important evolution in header bidding technology. While it's not the perfect solution for every publisher, its ability to scale bidder participation without impacting user experience makes it increasingly valuable in a complex programmatic ecosystem.

If you're considering a move to server-side header bidding, start by evaluating hosted solutions and possibly testing with a portion of your inventory to see how it performs for your specific use case.