Glossary term

SSAI (Server-Side Ad Insertion)

What is SSAI?

SSAI (Server-Side Ad Insertion) is a server-side technology that inserts ads into video content directly on the server before it is delivered to the viewer.

SSAI Notes

1. SSAI works by fetching ads from one or more ad servers and stitching those ads into the video content as a single stream. This stream is then delivered from the server or cloud to the user.

2. SSAI is used to insert advertising in connected TVs, set-top boxes, game consoles, and other consumer electronic devices that lack client-side capabilities and/or thwart ad blocking.

3. In SSAI, the video player can’t handle ad tracking like it does in client-side setups, and the ad-stitching server doesn’t see traditional ad tags. Instead, it tracks ads by using other methods to identify the device playing the ad.

How Does SSAI Work?

With SSAI, when a user requests playback, the server fetches targeted ads from an ad server, merges them with the content, and delivers the combined stream through a CDN.

Here is how it works:

Step 1. Ad Decisioning

The SSAI server requests personalized ads from an Ad Decision Server (ADS) based on user data, device type, content, etc.

Step 2. Ad Stitching

This part is the heart of SSAI: The server stitches the ads and content into a single, continuous stream, preventing ad blockers for a seamless playback experience.

Step 3. Manifest Manipulation

For HLS or MPEG-DASH streams, SSAI modifies the manifest file (e.g., .m3u8 or .mpd) to include ad segments.

Step 4. Encoding and Transmuxing (an extra step)

Ads and content might need to be encoded in compatible formats or transcoded to match the delivery format.
Step 5. Content Delivery via CDN

The final stitched stream (ads + content) is served to the viewer through a content delivery network (CDN).

Supporting Technique: Video Pre-Loading

Pre-loading refers to loading video content (or ads) in advance so it's ready to play without buffering. It can be applied to both the ads and the content.

Video pre-loading is NOT a part of SSAI itself, but:

• It enhances playback performance during SSAI delivery.
• A player may pre-load upcoming ad/content segments to reduce latency or buffering.
• It can be useful when SSAI is combined with client-side fallback or hybrid strategies.

Ad Stitching vs Stream Stitching

Ad Stitching

The process of combining ads with main video content into a single, seamless stream is called ad stitching.

Although it is typically done on the SSAI, it can also be emulated on the CAI (Client-side ad insertion). Ad stitching is mainly used to get a buffer-free, ad-block-resistant ad experience.

Stream Stitching

Stream stitching is synonymous with ad stitching when used in the ad tech context. However, It may also refer to more generally combining multiple video streams (e.g., content + promo + outro), not just ads.

For example:

Stitching a pre-roll ad, the main episode, and a branded end screen into a single HLS/DASH stream.

Term	Function	Where It Happens	Focus	Part of SSAI?
Ad Stitching	Merges ads with content into a single stream	Server or client	Monetization	Core component
Stream Stitching	Same as ad stitching, or merging multiple streams	Server	Seamless delivery	Core component
Video Pre-Loading	Loads content/ads before playback	Client (video player)	Performance	Optional/supporting
Ad Decisioning	Requests targeted ads from an Ad Server based on user/session data	Server	Ad targeting	Core component
Manifest Manipulation	Edits HLS/DASH playlists to insert ad segments in proper sequence	Server	Stream structure	Core component
Encoding and Transmuxing	Ensures content and ads use compatible formats and delivery protocols	Server	Playback compatibility	Core component

SSAI Benefits

• Better User Experience:Since the ads and content are seamlessly stitched together, transitions are smoother, and there are fewer playback interruptions.
• Ad Blocker Resistance: With SSAI, the stream comes as a single video file; it's nearly impossible for ad blockers to detect and block the ads.
• Device Compatibility: SSAI is versatile. It works across web, mobile, smart TVs, and CTVs without needing platform-specific SDKs.
• No Frequent Code Updates: Code-free integration eliminates the need for regular SDK updates or player-side modifications.
• Increased Ad Inventory: Because the ads aren’t loaded by the video player, more impressions get delivered, increasing revenue potential.

SSAI vs CSAI

Ads can be inserted into the content or stream in two ways: the first is SSAI (Server-Side Ad Insertion), which we are already familiar with, and the second is CSAI.

So what is CSAI? IS SSAI any better than CSAI? Let’s compare and find out.

What is CSAI?

CSAI (Client-Side Ad Insertion) is a method of delivering video ads where the video player on the viewer’s device is responsible for requesting, loading, and playing ads. Ads are inserted separately from the main content, often by making real-time calls to an ad server during playback.

CSAI gives more control to the ad server and supports advanced tracking, but is more vulnerable to ad blockers and can cause buffering between content and ads.

While SSAI stitches ads and content together on the server side, offering a smoother playback experience and better ad-block resistance, it limits client-side tracking capabilities and requires more backend infrastructure.

Aspect	SSAI (Server-Side Ad Insertion)	CSAI (Client-Side Ad Insertion)
Where Ads Are Added	On the server, before reaching the viewer	Inside the app or website on the user’s device
How It Works	Ads are combined with the video to form one smooth stream	Ads are loaded separately during the video
Playback Experience	Very smooth – no extra loading between ads and video	Can pause or buffer when switching to ads
Ad Blocking	Harder to block – ads look like part of the video	Easier to block – ad calls are visible to blockers
Device Compatibility	Works well across most devices and platforms	Needs specific support for each device or app
Ad Tracking	Limited – tracks at the server level	Advanced – allows detailed tracking on the viewer’s side
Setup Difficulty	More work on the server, but simple on the player	Easier backend, but complex app integration
Need for SDKs	No need – works without extra code on devices	Often needs SDKs or code updates for each platform

Overview

SSAI is the best for

• Seamless ad playback without buffering
• Ad blocker resistance
• Simple player integration (no SDKs needed)
• Cross-device playback (TVs, mobile, web)

CSAI is the best for

• Advanced ad tracking and measurement
• Quick setup on the server side
• Personalized ads based on real-time viewer actions
• Smaller-scale apps or MVPs that need fast ad implementation

SSAI in OTT and FAST Ecosystems

In both OTT (Over-the-Top) and FAST (Free Ad-Supported Streaming TV) platforms, SSAI is responsible for delivering monetized content seamlessly and at scale.

Here is what it does for both ecosystems:

SSAI In OTT Platforms

The most important thing that SSAI helps with is personalization. OTT providers get to deliver personalized ads without disrupting the viewing experience.

Since OTT platforms stream over the internet to multiple devices (smart TVs, mobile, web), SSAI ensures smooth transitions between ads and content by stitching them together on the server into a single, continuous video stream before it reaches the viewer.

Plus, SSAI’s technical infrastructure enables cross-device compatibility (no SDKs needed for each platform) and ad-block resistance (ads stitched directly into the stream). This makes SSAI ideal for SVOD/AVOD/HVOD services aiming for professional monetization and playback.

SSAI for FAST Channels

FAST services operate similarly to traditional linear TV, but are streamed digitally and supported by advertisements. For FAST Channels, SSAI enables seamless ad breaks (e.g., in live or scheduled programming, ads appear smoothly). It also allows the scalable delivery of ad-stitched streams, particularly needed when targeting large audiences.

And last but not least, SSAI helps with real-time monetization. Everything works without the need for complex client integrations. Since FAST channels run continuously, SSAI is preferred over CSAI to avoid buffering, SDK fragmentation, or ad blocking.

Why Choose SSAI?

• Delivers a TV-like ad experience with internet flexibility
• Simplifies ad delivery for multi-platform support
• Maximizes inventory fill by avoiding ad blockers
• Scales easily for both on-demand and live content