Ad Insertion for Streaming Monetization: SSAI vs. CSAI vs. SGAI (and When to Use Which Strategy) 

Coming out of our recent Wowza webinar on ad insertion, one theme was crystal clear: there’s no single “best” ad insertion method for every workflow. Server-Side Ad Insertion (SSAI) and Client-Side Ad Insertion (CSAI), and now Server-Guided Ad Insertion (SGAI), each shine in different scenarios. This guide distills the webinar’s takeaways and folds in current industry research so you can choose the right approach for your business goals, tech stack, and viewer experience.

What Is Dynamic Ad Insertion (DAI) and Why Does It Matter for Monetization?

Ad insertion is the underlying method by which platforms stitch or schedule ads into live, linear, or VOD streams. The overarching goal to drive revenue must always be balanced with the need to ensure a top-quality viewing experience. Most ad decisioning relies on IAB Tech Lab’s VAST standard to communicate ad metadata and tracking between players/servers and ad servers. Using the latest VAST (e.g., 4.3) helps with verification, viewability, and cleaner measurement handoffs across the chain. Dynamic ad insertion (DAI) is a strategy that allows organizations to incorporate more targeted, tailored ads that preserve immersion for viewers while attempting to maximize ROI.

SSAI (Server-Side Ad Insertion): Seamless Playback and CTV Reach

SSAI “stitches” ads into the stream in real time (or near real-time) on the server before delivery. Viewers get smooth transitions, and CTV/device coverage tends to be strong. SSAI is also more resilient to most ad blockers because ads are delivered as part of the same stream. Trade-offs include extra server work, careful latency budgeting for live, and the need to align impression counting with client-initiated measurement guidance. Interactivity and personalization at scale also become more difficult.

When SSAI Wins

• Live sports, FAST channels, and premium CTV where playback smoothness is non-negotiable.
• Broad device coverage, including older Roku and Smart TVs, withad blocker resilience.
• Centralized control of ad conditioning and failover for reliability at scale.

CSAI (Client-Side Ad Insertion): Flexibility and Easy Personalization

CSAI keeps ads separate from content. The player requests ads and handles insertion and beaconing locally, which makes personalization and measurement straightforward. It’s often the fastest to pilot because you can leverage your player SDK plus your ad server tags. However, CSAI also comes with its own drawbacks: higher susceptibility to ad blockers, potential playback disruptions, and more device-specific variance.

When CSAI Wins

• Web/mobile experiences where first-party data, client beacons, and rapid A/B testing are priorities.
• Smaller teams validating ad monetization quickly before investing in deeper stitching workflows.
• Quickly setting up and delivering personalized ads to single platforms

SGAI (Server-Guided Ad Insertion): The Best of Both Worlds

SGAI is the newest ad insertion strategy and represents a hybrid approach of SSAI and CSAI. The server “guides” ad opportunities (often via manifest signals/interstitials), while the player performs the final resolution, stitching, and measurement on-device. You retain SSAI-like smoothness and cross-platform reach but keep CSAI’s client beacons and personalization (especially powerful for low-latency live streams and evolving CTV standards). Because SGAI is newer, it has fewer broadcast implementation standards and some backward compatibility issues. To implement SGAI, you will need: compatible players and manifests (e.g., HLS interstitials), plus coordination with your ad server (e.g., GAM SGAI) and streaming stack.

When SGAI Wins

• You want SSAI-level experiences with CSAI-level measurement and targeting.
• You’re modernizing for low-latency HLS/DASH and plan to scale across CTV, mobile, and web.
• You need more control over failovers, pod construction, and ad-break logic on the player.

SSAI vs. CSAI vs. SGAI — How to Choose

Use this quick rubric to match the method to the moment:

• If ad-blocker resilience, smooth playback on CTV, and a stream that “just works” matter most → choose SSAI.
• If speed to market, client-side beacons, and fine-grained personalization/testing matter most → choose CSAI.
• If you want smooth playback with detailed measurement/personalization, especially for low-latency or mixed device fleets → choose SGAI.

Implementation Checklist (All Three)

• Standards: Adopt VAST 4.x; confirm ad server features for SSAI/SGAI (ad pods, wrappers, fallback).
• Markers & Manifests: Insert SCTE-35/EXT-X-DATERANGE or interstitials as appropriate; validate discontinuities and timing.
• Measurement: Plan for MRC/IAB-aligned client beacons—even with SSAI—to satisfy buyers’ attribution needs.
• Latency & QoE: Prefetch/pod-prime ads, normalize codecs/bitrates, and test ad failover paths to protect fill rate.
• Scaling: Verify ad server QPS limits, concurrency, and ad cache strategy for marquee live events.

Frequently Asked Questions

Does SGAI replace SSAI?

No. SGAI complements SSAI. Many teams blend SSAI (CTV/FAST) with SGAI (low-latency/mobile/web) or run per-platform strategies to maximize revenue while maintaining measurement fidelity.

Which approach yields the best fill rate and CPMs?

Fill and CPMs depend on supply, targeting, and reliability. SSAI often wins on reach and compatibility; CSAI/SGAI enable rich client beacons and data for buyers. The best outcomes come from eliminating timeouts, adding robust fallback pods, and standardizing tracking.

How Wowza Helps With Ad Insertion (SSAI, CSAI, and SGAI)

• Wowza Streaming Engine: Build modern SGAI workflows (including HLS interstitials and ad-marker insertion) with Engine modules and APIs. Our latest guides show how to structure SGAI for low-latency scenarios.
• Wowza Video: Monetize with CSAI or SSAI using your preferred ad server/network, ideal for rapid POCs and unified cloud workflows.
• Flowplayer (by Wowza): Add SSAI to the player layer where it fits your strategy, with plugins built for modern ad workflows.

Next Steps

Get the full breakdown of ad insertion strategies—SSAI, CSAI, and SGAI —with real implementation tips and pitfalls from our team.

• Watch the webinar recording: Deep dive into SSAI/CSAI/SGAI architectures, HLS interstitials, and monetization best practices.

• Talk to an expert: Want a tailored blueprint for your tech stack (low-latency live, CTV/FAST, or VOD)? Our solution architects can help you choose and implement the right approach for maximum monetization and measurement.