CSAI vs SSAI explained: understand how each ad insertion method impacts monetization, playback quality, ad personalization, and viewer experience across OTT, live streaming, FAST channels, and Connected TV platforms. Continue reading
Delivering tailored and seamless ad experiences has become crucial for marketers and content providers alike in today’s digital landscape, where advertising has substantially advanced. Ad insertion is essential for ensuring that advertisements are incorporated into video content in a way that increases user engagement and ad income. Ad insertion integrates advertisements directly into video streams at strategic points, maximizing engagement and revenue while maintaining playback quality. But when comparing CSAI vs SSAI, which approach works best for your business?
Ad insertion has become even more important for interacting with viewers across platforms with the emergence of live streaming, Connected TV (CTV) advertising, and the fact that more and more people now have access to multiple devices to access content. In this blog, we will compare two of the most standard ad practices on various parameters and decide what works best for your business.
Ad insertion, the process of integrating ads seamlessly into video content, enables advertisers to achieve these goals by providing a seamless viewing experience for users. By strategically inserting ads at appropriate moments within video content, ad insertion ensures that ads are relevant to the viewer’s interests and context. If we compare CSAI vs SSAI, both ad formats have their own pros and cons. While SSAI offers seamless ad insertion, CSAI gives more control to the client in terms of device and player selection. Let’s study both ad formats and then compare and decide what works best for you.
CSAI stands for Client Side Ad Insertion, and it is a method of delivering ads to the user where the client (user’s device) requests ads from the server when it reaches the ad marker point and the server then responds to it and delivers the requested ad and its various components like the ad media, tracking URLs, information about the ad, etc.
It is called client-side ad insertion because of the fact that the client or the player has control of what ad has to be played and when it has to be played.
CSAI works on ad-request setup and it follows the following steps to run the ads on the client’s device.
Step 1: The player downloads the content from CDN and starts playing the video, and in case of any pre-roll ads, they start playing before the actual video begins.
Step 2: When the video reaches the ad-marker points as defined by the video admin, the video player automatically pauses the video and sends an API call to the ad server requesting an ad to be played.
Step 3: The ad server, upon receiving the request, sends a VSAT XML file containing information about the ad such as the media file, tracking URLs, ad information, etc). VSAT or the video ad serving template, is a template defined by the Interactive Advertising Bureau to structure ad tags for effective analytics.
Step 4: The video player then uses that information and dynamically plays the ad on the device. Once the ad is complete, it starts the video playback again until the next ad insertion point.
So this is how the ads run when they are initiated via the CSAI model.
CSAI allows the ad producer to allow for a rich ad experience, as a lot of creative ads, such as surveys, overlays, and interactive media, can be automated using traditional client-side ad insertion technologies. This gives more creative freedom to ad creators.
With VSAT XML, tracking URLs are very easily inserted into the ad profile, enabling players to report every click, skip, etc thus giving better data for creating actionable insights.
Since the ads are delivered dynamically and not stitched beforehand with the video, it gives the ad runners more freedom to use the information and push the right ad at the right time.
CSAI is indeed a great ad insertion method, but it also comes with its own set of cons that you must know before you decide.
Since the player makes a call to the server whenever an ad is needed, several ad blockers have been designed to catch these API calls and block them. It’s a battle between the ad server and the blocker, and this incurs a loss to the advertiser.
Often, we have seen a video running smoothly, and then suddenly it stops for the ad, but the ad freezes as well. Since the player has to make a call to the server, this can result in latency and buffering if the ad server and the player are not tuned properly. This might frustrate the user, who might end up closing the video. Also, sometimes the ad quality is not the same as the video quality, and this sudden change in resolution creates a bad user experience.
SSAI or Server Side Ad Integration is another method of integrating ads to a video where the server does most of the heavy work and not the client. Here, the ads are directly stitched to the video file right at the server and then transferred to the client, thus eliminating any need for the client to make any API call for ad requests.
Step 1: In SSAI, the ad server stitches the main video content and the ad inventory creating a unified stream that includes both the ads and the content. The video is thus decorated with SCTE-104 markers, which represent the position of the ad break in the video stream.
Step 2: When the users click “play”, the video player starts getting the output in the form of HLS via the ad service. This HLS output also contains ad information.
Step 3: When the ad marker is reached, the ad insertion server starts transcoding the ad to match the bitrate of the playing video and thus stitches the ad dynamically to the video file.
Step 4: This creates a smooth video playback without any interruptions, and the ads also run smoothly.
With no API calls for ads that might be of different resolutions and give latency, SSAI ensures that the ad stream is directly stitched to the video stream and therefore maintains the quality of the video playback and provides an uninterrupted experience to the user.
Since the ads are inserted from the server side and the player does not make any API call to get the ads, most browsers and ad blockers find it very difficult to block such ads.
Ad vendors can stitch the ad to the stream, but they cannot guarantee its conversion, as there is no client-side verification of clicks. This makes it difficult to analyze ad performance.
Since the ads have to be stitched beforehand, a lot of dynamic ad delivery capabilities are restricted.
SSAI requires complex transcoding, stitching, and delivery, and this simultaneous ad + video delivery format is very complex to design and difficult to maintain.
| Parameter | CSAI | SSAI |
| Ad Delivery | Player requests ads | Ads stitched on server |
| Ad Blocker Risk | High | Low |
| Personalization | High | Moderate |
| Interactivity | Strong | Limited |
| Playback Smoothness | May buffer | Seamless |
| Ideal For | Web-based platforms | OTT, CTV, Live Streaming |
| Backend Complexity | Moderate | High |
Choosing between CSAI vs SSAI depends on factors such as your specific needs, campaign goals, and technical considerations. While CSAI can deliver a better personalized ad experience, SSAI, on the other hand, ensures seamless ad insertion with less ad-blocking threat.
Always consider factors such as ad tracking requirements, device compatibility, ad-format support, ad delivery, and the level of control before deciding which type of ad insertion you wish to select for your content.
Choose CSAI if:
Choose SSAI if:
For businesses running linear channels, FAST services, or scheduled live streams, ad insertion is only one part of the monetization equation. The bigger challenge is ensuring that content scheduling, ad break timing, and stream delivery work together seamlessly across devices.
This is where Muvi Playout becomes highly valuable.
Muvi Playout is a cloud-based playout solution designed to help broadcasters, OTT platforms, and FAST channel operators create and manage 24/7 linear channels without relying on traditional broadcast infrastructure. It allows content providers to schedule videos, define ad breaks, and create broadcast-grade streaming workflows from a single interface.
Get a free 14-day trial today.
The primary difference between Client-Side Ad Insertion (CSAI) and Server-Side Ad Insertion (SSAI) lies in where the ad insertion happens. In CSAI, the video player on the user’s device requests and plays ads separately. In SSAI, ads are stitched directly into the video stream at the server level before reaching the viewer.
Neither is universally better — the right choice depends on your streaming goals. CSAI offers better personalization and interactive ad formats, while SSAI provides smoother playback, better ad blocker resistance, and stronger performance for OTT and Connected TV platforms.
Most traditional ad blockers struggle to block SSAI ads because the ad is delivered as part of the video stream itself. Unlike CSAI, there is no separate client-side ad request that blockers can intercept easily.
For live streaming, SSAI is often preferred because it minimizes buffering and ensures smooth transitions during ad breaks. However, CSAI may still be useful when interactive ad formats are required.
Written by: Shivashish
Shivashish works as a content writer at Muvi. He has worked in domains like e-commerce, employee engagement, sports and entertainment. A poet by heart, Shivashish believes in creating quality content that is rich in information and easy to understand.
Add your comment