Content Monetization with Server-Side Ad Insertion

Client-side ad insertion (CSAI) is one of the most used techniques for monetizing video content. With CSAI, ads are loaded within the video player before they get displayed to the viewer. However, more than 26% of today’s viewers have ad blockers installed which prevent these ads from being loaded, resulting in the loss of revenue.

Telcos, broadcasters, and publishers are rapidly migrating from client-side to server-side ad insertion (SSAI). With SSAI, ads are loaded on the server side and then stitched into the content stream. This article discusses some of the issues with client-side ad insertion and why so many of these companies are moving to server-side ad insertion to solve them.


Today, the majority of ad inventory is served through clientside ad insertion. In this model, advertisement logic is handled completely by the video player and eventually executed by the web browser.
It works as follows:

  1. When an advertisement is about to be displayed, the video player triggers the web browser to ask an ad server which advertisement to play.
  2. After a series of lookups and exchanges, the ad server will respond with a suitable video ad template.
  3. The player will process the video ad template, causing a switch from the main video stream to the ad stream.
  4. Once the ad stream ends, the video player will switch back to the main video stream.

This is illustrated in Figure 1: Client-Side Ad Insertion (CSAI).

Client Side Ad Insertion process

Figure 1: Client-Side Ad Insertion (CSAI)

Whilst this approach has merit, there are some significant drawbacks impacting both revenue generation as well as viewing experience.

Losing Out on Ad Inventory Due to Ad Blockers

Ad blockers have become an increasingly popular method for end users to minimise or completely avoid online advertising. It is estimated by the Interactive Advertising Bureau (IAB) that 26% of desktop users and 15% of mobile consumers use ad blockers to prevent ads from playing. The resulting impact on a content publishers’ revenue streams is substantial.

Ad blockers are browser plugins that prevent specific requests from being performed by a web browser. In the CSAI case above, the ad blocker will identify the request done to the Ad Server in step 1 (Ad Server domain names are blacklisted by ad blockers) and prevent this request from happening. As a result, no advertisement will be played and the content video will continue playback.

While it is technically possible to detect the installation of ad blockers and in turn prevent the playback of the main content, this typically results in a degraded viewing experience and lower retention rates, which once again negatively impacts the bottom line.

Reduced Quality of Service

With client-side ad insertion, the video player typically switches between the main content and the advertisement. When this switch occurs, it is often preceded by a loading indicator. This is especially noticeable on mobile platforms, where there are strict video playback requirements and limited video playback capabilities.

There is a lot of video player logic involved in handling the steps involved in client-side ad insertion. While most video players today are able to correctly handle this, sometimes edge cases occur which result in playback stalls, failure to play ads, stream restarts, or a complete crash of the video player.

When video viewers are immersed in the content, they typically watch longer and more content. However, when any of these quality of service issues occur, a viewer’s immersiveness will be broken and there is a high chance that they will drop out early, negatively impacting ad completion rate and overall CPM.

Difficulties Monetizing Live Content

When looking at client-side ad insertion, video-on-demand (VOD) content typically gets monetized through pre- or mid-roll advertisements. This is often more difficult to orchestrate in the case of live streamed content where ad breaks need to be scheduled at precise timings in order to ensure viewers do not miss out on anything important.

Today, most publishers try to resolve this problem by introducing a secondary communication channel between the video player and their ad server. As soon as an ad break is triggered in the live content, a signal is send over this communication channel towards all the viewers. This signal in turn will trigger the video player to initiate a CSAI workf low, loading and playing an ad instead of the main content.

This approach has a number of disadvantages. Firstly, it typically gets custom built, making it error prone and expensive to maintain. Secondly, this new communication channel is vulnerable to ad blockers. Third, this communication channel can introduce additional overhead and affect the overall scalability of the streaming solution.


Luckily, help is at hand. In the case of server-side ad insertion, most of the ad handling logic is handled by a server-side solution.

Server-side ad insertion works broadly like this:

  1. When an advertisement is about to be displayed, the compatible streaming server will ask an ad server which advertisement to play.
  2. After a series of lookups and exchanges, the ad server will respond with a suitable video ad template.
  3. The streaming server will process this video ad template, stitching the provided advertisements in the content stream.
  4. The advertisements and content are delivered to the viewer as one continuous stream.

This is illustrated in Figure 2: Server-Side Ad Insertion (SSAI)

Server Side Ad Insertion process

Figure 2: Server-Side Ad Insertion (SSAI)

SSAI addresses each of the drawbacks associated with the traditional client side approach while offering new areas of efficiency and revenue generation potential.

A Solution to Ad Blocking

Where in the case of CSAI ads are loaded or blocked by a viewer’s browser, with server-side ad insertion requests to ad servers are made server-side before delivering the combined content to the viewer.

As a result, advertisements become an integral part of the content stream and ad blockers become unable to block the ad request or differentiate between real content and advertisements.

This results in an overall increase in played ad inventory and an overall increase in CPM.

Undisrupted Viewer Experience

When using CSAI the advertisement logic is handled by the video player. In the case of SSAI on the other hand most of this logic is handled by a compatible streaming server. The simplification of the workflow results in less edge cases or video player issues disrupting a viewer’s immersiveness.

Furthermore, because the advertisements are stitched within the content video and delivered as a continuous stream, viewers will no longer experience spinners when an ad break starts or ends.

The result is an increase in quality of service and overall viewer retention rate.

Monetizing Live Streams

Where ad scheduling in live streams can be challenging with client-side ad insertion, server-side ad insertion allows ads to be stitched frame accurately within the content video.

In order to do so, publishers will annotate their live streamed content with ad markers, indicating where ad breaks should start and end. On the server end, these ad markers will be processed, triggering the replacement of the content within the stream with relevant advertisements.

This greatly simplifies and standardizes the workflow for inserting ad breaks in live streams.


In this article we discussed some of the main hurdles of clientside ad insertion and how server-side ad insertion tackles these:

  1. Ad blockers are unable to block server-side ads, causing more ad inventory to be played by your viewers.
  2. Server-side inserted ads do not disrupt the viewer experience with spinners or player hiccups, causing an increase in quality of service and viewer retention.
  3. Complex ad scheduling scenarios become easier to control with server-side ad insertion, allowing ads to frame accurately be stitched in both live or VOD content.

So do not hesitate: Migrate to server-side ad insertion and increase your CPM. This migration is optimal when combined with the best of breed video playback solution, THEOplayer. Get in contact now and experience how our team of video experts can help you.

This article was published in the March 2017 Streaming Media Superguide: Monetisation & Ad Insertion.

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