Ad Server vs. SSP – What’s the Difference


Digital advertising is complicated. That’s an undeniable fact. It moves quickly, changes often, and it boasts more three-letter abbreviations than the average government bureaucracy. For these reasons, different things are often confused with one another. For example, for anyone new to the industry, the difference between an Ad Server and an SSP (Supply-Side Platform) can be nebulous at best.

And that’s what we’ll be addressing today.

The Ad Server and the Supply-Side Platform both play critical roles in the modern programmatic digital advertising system – but they’re very different tools with very different jobs.

Certain SSPs, however, have been slowly introducing features that used to be the domain of Ad Servers. Further, a select few Ad Servers are now integrating some SSP capabilities into their offerings.

In this way, they act as both an Ad Server and an SSP.

It’s this blurry demarcation that can make understanding these two different services even more difficult.

But even if a couple of players are combining the two, the services themselves are quite different.

In a rush? Skip straight to the essentials here.

What’s an Ad Server

The Ad Server is one of the foundational technologies of the modern digital advertising ecosystem.

The idea behind the Ad Server is relatively simple. It’s a server that exists to manage, store, and, yes, serve your ads.

Back in the early days of the internet, ads would be hardcoded into the site. That means that the images and the text that comprise a given ad would be written directly into the HTML of a page.

Once the ad had run its course, however, the site owner would have to make direct changes to the code itself in order to launch a new ad. Naturally, this was extremely inconvenient.

This process was a major limiting factor to the growth of the digital advertising industry and, in order to address this problem, the Ad Server was born.

The Ad Server is a fairly straightforward concept.

Rather than putting the ad content on the site itself, a publisher could dedicate space on the site to ads, and then actually serve those ads dynamically from another server.

In this way, publishers could implement new ads and end old ones without having to make any changes to the site itself.

As digital advertising has developed over the years, Ad Servers have grown more complicated and more feature-rich. Now they help publishers track data, implement Frequency Capping, and do a host of other things.

Of these things, perhaps the most important for today’s publishers is the ability to integrate into Supply-Side Providers (more on them later).

One thing to note is that publishers generally only have one Ad Server. Or at least just one Ad Server per site or digital property.

Self-Hosted vs. Hosted Ad Servers

There are two kinds of Ad Servers. Those you host yourself and those you don’t.

Hosted Ad Servers are Ad Servers that aren’t really yours. It’s a service someone else is providing for you.

You go online, sign up for the service, and follow the steps to integrate the Ad Server into your current system.

Hosted Ad Servers are the most hassle-free as the service provider sets them up, updates them, and maintains them. You just have to focus on the content and making sure that your site is correctly set up to receive the ads that they serve.

However, advertisement is often 100% of a publisher’s income. So hosting your ad server with someone else is giving up a lot of control.

You don’t have full control of your server. This means you don’t have full control of your data. Further, your ability to customize the server to fit your needs is limited by what the Host allows you to do.

For some publishers, especially bigger ones, these limitations can drive them to set up their own, self-hosted Ad Servers.

Self-Hosted Ad Servers are 100% under the control of the publisher. With a self-hosted server, a publisher can make any modifications they think necessary for the better functioning of their site and the maximizing of revenue.

Further, their data remains entirely under their control, rather than having to trust a third-party to collect and store it.

The downside of self-hosted servers is that they can require a lot of maintenance. Whereas a provider will have a dedicated team of professionals making sure that everything is running as it should be, with a self-hosted Ad Server, that’s all up to the publisher.

Updates, integration, maintenance – it’s all falling to the publisher with self-hosted ad servers. This means they either need to have staff capable of these things or pay a service provider to maintain the server.

As such, Self-Hosted Ad Servers tend to be the domain of two groups: techies that are up for the challenge and large publishers that have the resources to hire the required expertise.

Popular Hosted Ad Servers

For most people reading this article, a Hosted Ad Server is probably going to be the best solution. They are far easier to set up and require significantly less maintenance.

There are many Hosted Ad Servers out there, so here’s a list of 5 to help you get started with your search.

Popular Self-Hosted Ad Servers

Are you technically inclined? Are you a publisher with very particular needs? Do you jealously guard your data? Are you up for a challenge? If you answered yes to any of these questions, then setting up a Self-Hosted Ad Server might be for you.

The Open-Source self-hosted Ad Server segment is dominated by one project: Revive.

Formerly known as OpenX, Revive Adserver is the giant of the self-hosted Adserver world. Installation can be tricky and complicated, especially compared to just using a hosted server, but it gives you much more control.

One of the benefits of Revive is that there is an entire community of developers out there producing plug-ins for the Ad Server. So the potential for customization with Revive is very high.

If you like what you’re reading about Revive, but aren’t keen on installing, hosting, and maintaining your own Ad Server, then you’re in luck: they have a hosted platform as well.

The price of entry, $10 per month, is relatively low, so if you want to get familiar with the platform before pulling the trigger on self-hosted, this is a good option.

What’s an SSP

So that’s what an Ad Server is. So what’s an SSP then?

A Supply-Side Platform is a service that helps websites sell unused ad space. These services generally employ a technology known as Real-Time Bidding to sell ad space on a per-impression basis.

This means that when a user lands on a page, the site contacts the Ad Server and pulls the ads to be served. Often, direct clients (if the publisher has any) won’t have bought all of the ad space on the entire site.

Nevertheless, the publisher wants to monetize all of their available ad space for every single pageview.

With the development of programmatic advertising, this became possible. From the publisher’s end, the process looks something like this:

  1. A user arrives on the site
  2. The page calls its Ad Server so it can display whatever ads are already bought
  3. Some ad space remains, so a bid request is sent to the Supply-Side Provider
  4. The Supply-Side Provider then auctions the bid off through an Ad Exchange where Demand-Side Platforms and Ad Networks bid on it
  5. The winning bidder then sends its advertising material to the site’s Ad Server
  6. The Ad Server then serves the ads on the publisher’s site

The SSP is the publisher’s portal into this whole system. It allows him to sell extra ad space in real-time, thereby letting him maximize the value of each pageview.

So what’s the difference, again?

So, as you can see, SSPs and Ad Servers are two separate services.

The Ad Server is the foundation of a publisher’s monetization of his site through advertising. It allows him to serve ads on his site. Ad Servers also provide a number of tools to help manage his ads.

The SSP, on the other hand, gives the publisher a means of selling his inventory (unsold ad space), rather than a means of actually preparing and serving the ads on his site (the domain of the Ad Server).

So these are two complementary, but quite different services.

Where the lines start to blur

As often happens in the modern AdTech industry, the boundaries between the various services can be blurry. Certain Service-Side Platforms have begun to offer hosted Ad Server services allowing them to becomes something of a package deal.

This, however, doesn’t change the fact that Ad Servers and SSPs are very different services. In this case, a company is merely providing two distinct services at the same time.


The alphabet soup of terms that exist within this industry can make it difficult to break into for new people. The fact that some companies provide multiple services can make it seem like those services are one and the same and that the terminology is redundant.

Sometimes this is the case. But it isn’t here.

The difference between a Service-Side Platform and an Ad Server is clear. One prepares and serves the ads for a specific publisher’s site. The other allows the publisher to find buyers for unused ad space through a programmatic auction on a per-impression basis.

Quick Recap (TL;DR)

Although relatively frequently confounded with one another by newbies, Supply-Side Platforms and Ad Servers are entirely different services with separate roles to play in the serving of ads.

Supply-Side Platform (SSP) – This is a platform that a publisher can use to sell inventory (unsold ad space). It uses a technology called Real-Time Bidding to find buyers for the inventory (usually Demand-Side Platforms and Ad Networks). SSPs sell on a per-impression basis. A publisher can use multiple SSPs.

Ad Server – This is the server that stores, prepares, and serves ads on a publisher’s website. The publisher can host this server himself, or he can use a third-party service that will host and manage the server for him. A publisher generally only has one Ad Server.

Some SSPs are now offering services that would traditionally be a part of an Ad Server. Some are offering hosted Ad Servers entirely integrated into their SSP. Nevertheless, these are two different services.

Mobinner is a high-performance Demand-Side Platform. Since 2017, we’ve been helping customers build brands, acquire users, and drive conversions. See what Mobinner can do for you.

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