For years, the digital advertising industry has been quietly rewiring itself. The shift from client-side to server-side technology sounds technical—because it is—but at its core, it represents something more fundamental: a reckoning with the limits of the old way of doing things.

When Browsers Became Battlegrounds

The traditional model was straightforward enough. Everything happened in the user's browser: the auction logic, the calls to ad exchanges, the timeouts, the logging. Publishers could see exactly what was happening, when it was happening, and why.

But transparency came with a price tag measured in milliseconds.

As publishers added more partners to their monetisation stack, browsers buckled under the weight. Pages slowed. Users waited. The math became unavoidable: more partners meant more lag, and eventually, a worse experience for everyone.

The Promise—and the Reality—of Moving to Servers

The server-side solution sounds elegant. Move the heavy lifting off the browser and onto a dedicated server. The user's browser makes one lean call, and everything else, the auctions, the requests to ad exchanges, the selection of winners, happens elsewhere, out of sight.

The result, in theory: faster pages, infinite scalability, and the ability to enhance bid requests with richer data.

In practice? It's far more complicated.

Servers don't have access to the granular information that browsers do. No cookies. No viewport context. No-user sync. No direct signals from the page itself. That gap is where the real engineering challenge begins.

The Question That Changes Everything

Building a server-side system forces you to answer one deceptively simple question: What exactly should go into each bid request?

The answer determines whether the system works at all.

A high-performing setup requires bid requests that are rich, accurate, and customised to what each ad exchange expects. But there's no standard template. It requires:

• Direct collaboration with each exchange to understand their data requirements and how they interpret signals
• Complex data pipelines that transform raw inputs—converting IP addresses into geolocation data, for instance
• Constant iteration to work around incomplete or outdated documentation
• Testing, retesting, and fine-tuning to ensure all the right fields are passed

At Pubstack, this process took weeks of testing with each partner. What made this possible was deep technical collaboration with every exchange. When partners see that the goal is better performance for everyone—not competitive advantage—they open up about what actually works. Exchange-owned server-side products rarely reach the same level of integratios. Competitors don’t tend to help each other win.

The Infrastructure No One Talks About

Then there's the infrastructure problem, which is massive.

A server-side system doesn’t just handle incoming calls; it also triggers many more outgoing requests to ad exchanges, multiplying the load on bandwidth and compute resources. This becomes a question of cost and speed, requiring systems that can handle enormous volumes without breaking or slowing down.

At scale, this becomes a question of cost and speed, requiring systems that can handle enormous loads without breaking or slowing down.

Geography adds another layer of complexity. Traffic from the US needs to be handled by US-based servers, not just for speed, but for cookie matching. When a US user's request gets routed to a European endpoint, the match tables diverge, and revenue drops.

Pubstack has seen this firsthand. Each time the company deployed new server clusters in the US or Asia, exchange revenues in those regions jumped four to five times, simply because requests were finally being routed to the right place.

It's a reminder that server-side performance depends as much on where your servers are as on how smart your code is.

Why Independence Matters

Most server-side products are built by ad exchanges themselves. That creates two problems.

First, they're not neutral. An exchange-owned platform has every incentive to favour its own bids.

Second, they're not collaborative. Competitors don't share optimisations or improvements with one another.

A neutral technology takes the opposite approach: working with every exchange to improve their performance, ensuring fairness in every auction, tailoring bid requests to each partner's needs, and deploying infrastructure designed for speed and transparency.

A Shift in Mindset

Moving from client-side to server-side isn't just a technical migration. It's a shift from a simple, transparent, browser-driven world to a distributed, data-driven architecture where every millisecond and every data field matters.

That's why neutrality and collaboration matter more than ever.

The best solutions bring together the performance and scalability of server-side technology with the trust, transparency, and control that publishers need to run their businesses.