DAI Implementation Methods: A Quick Guide to Server-Side Ad Insertion (SSAI) and Client-Side Ad Insertion (CSAI)

If you’re still undecided about personalizing ads in live streams, FAST channels, or VOD, now is the time to take action. The Advertising Video on Demand (AVOD) market is booming, expected to grow from roughly $48.8 billion in 2024 to over $71.6 billion by 2030 with a ~6.6 % CAGR. 

The core value of AVOD platforms hinges on dynamic server-side ad insertion (SSAI), which inserts ad markers server-side to bypass ad blockers. With over 60 % of VOD content now delivered via OTT platforms, SSAI adoption had been growing steadily, by ~40 % since 2020 to 2024, as more providers shift toward ad-supported models. 

And to top it off, audiences —  from Gen Z to older generations —, are increasingly okay with ads, as long as they’re relevant and not too intrusive. In fact, MNTN research reports that 66 % of U.S. viewers prefer ad-supported services, and younger viewers being the most accepting when it comes to live content.

This article is a comprehensive guide to Server-Side Ad Insertion (SSAI), where and why it matters for OTT platforms. But before we dive into how SSAI works, let’s take a step back and unpack the broader concept it fits into: dynamic ad insertion.

What is Dynamic Ad Insertion (DAI)?

Dynamic Ad Insertion (DAI) is a broad monetization technique where video ads are inserted into a stream dynamically, in real time, and personalized per viewer.

• DAI enables targeted advertising based on user data (location, device, behavior).
• Ads can be inserted into live streams, VOD, or time-shifted content.
• It supports pre-roll, mid-roll, and post-roll formats.

Think of DAI as the what—the method of dynamically inserting ads into content.

DAI Implementation Methods

What is SSAI?

Server-Side Ad Insertion (SSAI) is one of the delivery mechanisms for DAI. It handles the technical how of stitching ads into the video stream on the server before it reaches the viewer.

• Ads are stitched into the video stream itself, making it appear as a single continuous stream.
• Because the ads and content are delivered together, SSAI bypasses ad blockers.
• It works well across devices, especially in environments where client-side ad SDKs are unreliable (e.g., smart TVs, Roku, or legacy mobile devices).

All SSAI is DAI, but not all DAI is SSAI. DAI can also be done on the client side, which comes with limitations (e.g., ad blockers, device SDK compatibility).

Why is SSAI important?

SSAI is important because it allows for a broadcast quality like experience. It removes the ability for ads to be blocked, and is a highly scalable solution to monetize live video as well as video on demand (VOD).

What is CSAI?

While SSAI handles ad stitching server-side, Client-Side Ad Insertion (CSAI) takes the opposite approach: ads are inserted by the viewer’s device or app, typically using an SDK (e.g., Google IMA or FreeWheel).

• Ads are loaded separately from the content stream and triggered at defined ad break points (pre-, mid-, post-roll).
• The player pauses the main video, requests the ad from an ad server, plays it, then resumes the content.
• Because the ads are delivered in separate HTTP requests, CSAI is vulnerable to ad blockers.
• Works best on platforms where SDK integration is stable and consistent, typically mobile apps and browsers.

SSAI works where client side doesn’t

As said before, SSAI removes the ad blockers and improves live TV ad insertion capability, very similar to traditional TV break structure, but enhanced with targeting. Ads are stitched into the video stream on the server, making them invisible to client‑side filters. 

With a ‘cookieless’ world, where traditional browser cookies are no longer used to track users for privacy reasons, SSAI allows you to target users with dynamic ads by using non-cookie data (IP address, device type, and content context). This information is fed to the ad server so targeted ads can be stitched into the individual user’s stream in real time.

The SSAI system then manipulates the stream manifest—a roadmap that tells the video player what to play, in what order, and from where. This allows platforms to deliver contextually relevant ads to each viewer. For example, someone on a smart TV in California might see a car ad, while a mobile viewer in Vermont could get an ad for coffee.

What’s the technical workflow for this process? SSAI systems rely on SCTE-35 markers or server-generated signals to mark upcoming ad breaks. SCTE‑35 is a signaling standard, like a flag embedded in your live stream. The ad server makes a call based on viewer metadata and delivers creatives tailored to that pod, a block of time carved out in the stream where one or more ads will play. The ad server responds with compatible creatives, ideally transcoded to match the viewer’s bitrate, so if you are streaming in 4k, an HD ad will look odd.

SSAI vs CSAI: Key Differences

Here’s how SSAI and CSAI compare when used as DAI methods:

SSAI for VOD

SSAI for VOD requires a bit more technical involvement on the player side, but pays off in precision and scalability. When a user clicks to play a VOD asset, the system makes an ad request to the ad server.

Any programmatic advertiser wants to know if the user viewed the ad. The advertisers typically need a beacon to fire off from the player that tells the ad server (and the advertiser) that the ad was played. Beacons get fired every 5 seconds, so it is known that the ad has been viewed. This usually needs an SDK integrated into the player.

For mid-roll ad breaks, the SSAI server needs clear instructions about where to insert them. This can be done by adding SCTE 35 markers to the VOD files or utilizing VMAP (Video Multiple Ad Playlist), which is a file that specifies how many mid-rolls to insert and at what time offsets. 

SSAI for Live TV

Live streaming is where SSAI works best, especially when a consistent experience matters. But there’s a catch.

If you’re pulling in live TV feeds from satellite sources, those feeds often come without the SCTE‑35 markers that tell the system where ad breaks are supposed to happen. Without those markers, the SSAI platform doesn’t know when or where to insert ads. 

When that happens, you need ad‑marker reconstruction tools that detect ad slots. Then, those ad detection tools can insert SCTE‑35 markers back into the stream, so the SSAI knows when to jump in and replace the original ads.

Once those markers are in place, SSAI takes over: it uses them to insert targeted ads at exactly the right moment, in real time, without interrupting the live broadcast.  

Monetize Smarter with SSAI 

SSAI is infrastructure rather than an ad tech feature. It enables targeted, broadcast-grade monetization for VOD, live TV, and FAST channels. Early adoption pays off. As markets develop, publishers and operators who embrace it early stand to reap the most benefit. 

Whether you’re running a global FAST network or launching VOD in a single region, Nora, Setplex’s future-proofed OTT middleware, helps manage and monetize your entire service, from ad delivery to subscriber engagement, with the infrastructure and tools needed to scale.

Nora is designed to support AVOD, SVOD, TVOD, FAST, and hybrid models with real-time flexibility. It integrates custom content workflows, enabling operators to deliver targeted ads with precision across any platform or device. 

Get in touch with Setplex to see what Nora can do for your streaming or video service, or see the Nora Spec Sheet for more information. 

FAQ: Server-Side Ad Insertion (SSAI)

What are the different types of ad insertion?

There are two main types: server-side ad insertion (SSAI) and client-side ad insertion (CSAI). SSAI stitches ads directly into the video stream on the server, while CSAI loads ads separately on the user’s device.

What is dynamic ad insertion?

Dynamic ad insertion (DAI) is a method of delivering targeted ads in real time based on viewer data. It works for live streams, VOD, and time-shifted video content.

What is the difference between SSAI and CSAI?

SSAI inserts ads server-side, delivering a seamless, ad-blocker-resistant viewing experience. CSAI inserts ads client-side and is more vulnerable to ad blockers and playback issues.

Can SSAI be used for live streaming?

Yes. Server-side ad insertion (SSAI) is ideal for live streaming, allowing video ads to be stitched into live streams in real time, without buffering or ad-blocking issues.