How does Server-Side Ad Insertion (SSAI) work?

When it comes to ad delivery in Connected TV (CTV) and Over-The-Top (OTT) environments, there are two ways to insert advertising into the content: Client-Side Ad Insertion (CSAI) and Server-Side Ad Insertion (SSAI). In this article, we are going to focus on Server-Side Ad Insertion (SSAI). We’ll take a deep dive into how this technology works and why it is the preferred method in large parts of the CTV industry. We’ll also discuss one of the major challenges and ways to tackle that.

Client-side ad insertion (CSAI) is a method by which the video player, located within an app or a website, requests an ad from an ad server. When the ad server has received the ad request from the video player, it sends an ad and displays it within the video content.

SSAI is a method of delivering video ads by attaching them directly to video content on the server side instead of the client application or video player, as is the case with client-side ad insertion (CSAI).The user experience with SSAI can be compared to traditional TV ad breaks, as there is a smooth transition from video content to the ad break. The viewer is not waiting for the ad to load, and it’s a continuous viewing experience without pauses or interruptions between content and ads. The big difference between the user experience compared to traditional television lies in the advertising side, since SSAI offers the possibility of delivering fully personalized and relevant advertising to each user. This high user experience is the main reason why most of the industry is opting for this type of solution that offers the user a smooth experience between content and advertising. From a technical perspective, delivering content and advertising in the same flow initially posed challenges regarding the targeting of these ads, which are solved by combining two key pieces: manifest manipulator and ad server.

  • Manifest manipulator: responsible for personalizing the video experience for each viewer, presenting different ads to different viewers.
  • Ad server (or Ad decision server): essential for determining which ad to deliver, whether it is a direct or programmatic campaign through its connections with the different Supply-Side Platforms (SSPs), depending on the parameters of the call, collecting delivery data and different campaign KPIs.

As a summary, this would be an example of an SSAI architecture:

  1. The user’s player makes a video file request to the Content Delivery Network (CDN). At the same time, it requests the manifest to the Manifest Manipulator service.
  2. A modified Manifest is generated with the information of the file to be played and with all the necessary information to play the ads during ad breaks.
  3. All this information is sent to the packager and packaging and encoding are done if needed.
  4. The CDN will deliver the stream with the requested video and inserted ads to the user.
Server Side Ad Insertion SSAI

As previously mentioned, the industry is mainly choosing SSAI solutions.  Here are some of the main reasons for this choice:

  • Better user experience
  • increases the volume of inventory: as the user doesn’t make calls to the ad server, it’s impossible to use ad blockers.
  • no regular code updates required: SDKs are not needed thanks to code-free integration.


Unfortunately, there are not only advantages; the fight against fraud is one of the main challenges. High CPMs and high interest from advertisers have made CTV a place where fraud is rampant.

However, the main anti-fraud companies in the sector already have developed tools to try to minimize fraud and increase confidence in advertisers in this environment.

Aware of the great concern of advertisers about this issue, some streaming companies have developed internal solutions. This is the case of Roku, which launched its Watermark 1.0 solution in 2022 to prevent fraudulent impressions.

With this tool, Roku verified that the requests came from its own devices and not from bots or networks that generated fake device identifiers.

Roku has recently updated its solution to Watermark 2.0. This new version detects false impressions at the application level as well as at the device level. It is also possible to send the watermark throughout the programmatic offer chain, which guarantees that the impression does not come from a fraudulent system.

The number of companies adopting this solution is growing with companies like PubMatic, DoubleVerify, Google, Innovid, Magnite and Human among others.

Over the next few years, we will see the number of solutions, whether proprietary or third-party, increase until fraud rates decrease in CTV environments.
From its side, IAB continues to promote solutions such as, seller.json, SupplyChainObject, or ads.cert 2.0. that provide a complete set to prevent fraud in CTV and in the whole digital ecosystem.

There is still a long way to go, while the tools continue to be refined and the market adopts certain standard measures, the most effective practice is to generate deals (either PMP or Guaranteed) with trusted partners who directly control the inventory, or with as few intermediaries as possible so you can maintain control over when, in what formats, and in what context your ads are delivered.

This article was originally published in Spanish by Programmatic Spain here.

by Cristina Iturralde

COO, Agile Ads