CSAI vs SSAI: Client-side & server-side Ad insertion methods

September 20, 2024
Video Education
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The first video advertisement aired in 1941 during a baseball game on the World’s Newest Broadcasting Television, one of the first television stations in the United States. It was a 10-second commercial for Bulova watches, marking the start of video advertising. This ad cost around $9,000 at the time and reached an audience of approximately 4,000 viewers.  

As video advertising evolved with television, so did the methods to deliver those ads. Initially, Server-Side Ad Insertion (SSAI) was the primary method. With advancements in technology, Client-Side Ad Insertion (CSAI) became popular. Recently, with the growth of streaming services, SSAI became popular again. So, SSAI was first, then CSAI came along, and now SSAI is back in style. But it depends on what's most important to your business and the viewers.

What will you choose?

As a developer, choosing between CSAI and SSAI means weighing trade-offs like flexibility, complexity, and control. Each approach has its unique characteristics and benefits, and finding the right fit can make all the difference in how smooth (or bumpy) your ad delivery is.  

According to Samba TV’s State of Viewership Report 2024, U.S. households watched a record-high level of OTT content in the first half of 2024, a 40% increase from 2023. Major streaming platforms have launched ad-supported options, with over half of SVOD sign-ups in 2024 driven by these ad-tiers. Additionally, 33% of U.S. viewers now use FAST services.  

Antenna Insights June 2024, SVOD share of sign-ups.

When we look at Antenna’s June 2024 report on subscription share in the past few years, ad-supported plans have seen a lot of action. In the first quarter of 2024, ad-supported plans made up 57% of new sign-ups, compared to 39% for ad-free plans. This shift has been evident over the past couple of years, with ad-supported plans gaining ground each quarter.

What is digital ad insertion?

Digital ad insertion is all about blending ads into your video content without annoying your audience. The right choice of ad delivery can enhance the viewing experience and keep those viewers engaged without disrupting their experience.

Ads can be a helpful way for developers to earn revenue early on without charging users directly. By using ads wisely, you can keep your content free while focusing on growing your project.

Digital ad insertion comes down to two main methods: client-side ad insertion and server-side ad insertion. With CSAI, ads get dropped right into the viewer’s device, giving you flexibility and interactivity. On the other hand, SSAI integrates ads directly into the content stream on the server, creating a smoother, more TV-like experience.

What is client-side ad insertion?

CSAI is like adding ads to a video playlist on the user's device. The ad content is delivered to the browser or app, which handles loading, playing, and tracking each ad. This method gives developers a lot of control over the ad experience, from targeting and tracking to better creative adjustments.

Here’s how it works: When a viewer clicks play, the video player requests both the content and the ads separately. The player then integrates the ads with the main content, displaying them before, during, or after the video. CSAI is a popular choice for platforms needing flexibility and interactivity—think personalized ads, clickable banners, or customized overlays during live streams.

What is server-side ad insertion?

SSAI, also known as "ad stitching," merges ads directly into the content stream on the server before it reaches the viewer. Think of it as creating a video stream that feels like one continuous piece of content ads included. This method minimizes interruptions and makes it much harder for ad blockers to interfere.

Here’s the technical rundown: The server prepares a single video stream that combines both content and ads. When the viewer hits play, everything flows smoothly from the server to the screen, without extra requests to fetch ads. SSAI is ideal for on-demand content and live streaming where a buffer-free, broadcast-like experience is key, ensuring ads reach viewers without missing a beat.

Infographic on how client side and server side ad insertion work.  September 19, 2024 at 10:43 AM

Key differences between CSAI and SSAI

Aspect Client-side ad insertion Server-side ad insertion
Ad delivery location Ads are inserted into the video stream on the client side, usually in the browser or app. Ads are inserted on the server side before the video reaches the client.
Flexibility Offers more flexibility for dynamic ad insertion and targeting based on user behavior. Less flexible in ad targeting; ads are inserted into the stream at the server level.
Ad blockers Vulnerable to ad blockers, which can prevent ads from being displayed. More resistant to ad blockers.
Latency May introduce latency or buffering as ads are inserted in real-time. Typically results in lower latency since ads are pre-inserted into the stream.
User experience Can affect user experience with potential interruptions or buffering when ads are played. It provides a smoother viewing experience.
Implementation complexity Easier to implement and manage, especially for smaller or simpler setups. More complex to implement, often requiring sophisticated infrastructure and costly server resources.
Analytics Allows for detailed analytics and tracking of ad performance on a per-user basis. Analytics can be more challenging as ads are part of a continuous stream.

What are Ad blockers? How it works in Video?

Advantages of CSAI

CSAI offers flexibility in how ads are delivered, allowing you to adjust creatives, target specific audiences, and control ad placements in real time. It’s simple to set up and offers powerful analytics, providing clear insights into viewer behavior and ad performance.

By personalizing ad content for each viewer, CSAI boosts engagement and cuts down on ad fatigue. This customized experience helps brands connect better with their audience, leading to stronger conversion rates.

Challenges of CSAI

CSAI is not without its downsides. Ad blockers can disrupt the ad delivery, leading to reduced viewability and lost revenue. Plus, handling ads on the client side can introduce latency, shifts in video quality, and buffering issues, which can frustrate viewers and impact their overall experience.

On top of that, CSAI requires custom development for each operating system where the ads will run, adding extra complexity to the process.

Advantages of SSAI

SSAI enhances the user experience by creating an uninterrupted, buffer-free viewing session and ensures better ad viewability since ads are integrated directly into the stream. It also stands up well against ad blockers, making it harder for them to prevent ads from being shown.

With SSAI, ads are stitched directly into the video stream on the server before it reaches your device. There are no separate requests for ads made from your browser, which is what ad blockers typically target. Since everything is bundled together as one continuous stream, ad blockers cannot differentiate between the content and the ads, making it harder for them to block the ads.

Challenges of SSAI

SSAI can be complex to implement due to the need for sophisticated server-side processing and integration. It also tends to come with higher server costs and technical demands, which can impact on your budget and infrastructure.

After considering the advantages and challenges of CSAI and SSAI, it is important to understand how native advertising fits into the equation. Native ads are displayed along with the surrounding content, providing a unique way to engage users. This section will explain what native advertising is, the types available, and how it can improve your ad strategy.

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What is native advertising?

Native advertising is a form of paid content that matches the design and style of the platform it appears on, blending naturally with the user experience. Unlike traditional ads that can interrupt and feel out of place, native ads fit right in, making them less likely to disrupt the viewer.

As digital audiences face ad fatigue and ad blindness, native advertising has become more important in helping brands connect with their audiences in a way that feels relevant and engaging. Unlike standard ads that stand apart, native ads offer a more integrated approach, capturing attention without breaking the flow of content

Native advertising by Nike on Instagram.

Nike has found a way to connect with its audience on Instagram by creating engaging, visually appealing content. One example is their sponsored posts, where athletes are shown using Nike products during their workouts or daily routines. These posts blend right into users’ feeds, making them feel more like regular content than traditional ads. By using high-quality images and relatable moments, Nike grabs attention while promoting their brand.

They also partner with influencers who show off Nike gear in real-life settings. These posts, marked as “Paid Partnership,” stay transparent but fit naturally into the influencer’s style, helping build trust with their followers. This strategy boosts Nike’s visibility while showing people how their products can be part of everyday life

Types of native advertising

Infographic on types of native advertising.

  1. In-feed ads:
    These ads are designed to blend into social media feeds or news articles, appearing as part of the content users are already browsing. They can be a wonderful way to capture attention without feeling out of place, but if done poorly, they can still feel like a disruption and risk being ignored.
  1. Sponsored content:
    Sponsored content includes branded articles, blog posts, or videos created to offer value while subtly promoting a brand. It works well for both brands and publishers by delivering content that audiences find useful or interesting, helping to build trust while promoting a product or service.
  1. Recommendation widgets:
    These are typically found at the end of articles or in sidebars, suggesting related content or products. They are effective for keeping users engaged by offering them more of what they are interested in, which can improve click-through rates. However, irrelevant, or overly promotional content in these spots can reduce engagement.
  1. Promoted listings:
    Common on e-commerce sites and search engines, promoted listings appear alongside or above organic search results. They increase visibility and can drive traffic, but if not carefully targeted, they can feel intrusive or miss the mark with users, impacting their experience.
  1. In-ad with native elements:
    This type integrates native elements like images or videos into standard display ads, making them look and feel more like part of the site or app content. When done right, they can improve engagement by aligning with the platform’s look and feel, but they still carry the risk of being skipped if users detect them as ads too quickly.

Summing up…

Integrating CSAI or SSAI into your ad strategy requires thoughtful consideration, and FastPix’s video API simplifies the process with features like accelerated uploads and adaptive bitrate streaming. With these features, you can ensure your ads along with video reach viewers without delays or interruptions, regardless of the method.

With advanced capabilities like multimodal indexing, speech-to-text translation, and AI-driven video summaries, FastPix lets you refine your content more for a better viewing experience.  

Sign up today to explore how FastPix’s video API can elevate your streaming experience.

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