SGAI Explained: Server-Guided Ad Breaks vs. Interactive Ad Layers

SGAI means server-guided ad insertion, and the term is used in two ways. Google Ad Manager, AWS Elemental MediaTailor and the HLS Interstitials standard use it for ad breaks that a server schedules and the player stitches on the device. StreamLayer SGAI uses server-side decisioning to guide nonlinear, pause and interactive ads rendered by an SDK alongside the stream.

What is server-guided ad insertion for ad breaks?

In the break-based meaning, a server decides which ads play and tells the player when to switch to them. The player then fetches the ads as separate media and plays them in place of, or next to, the content.

This sits between two older methods. With server-side ad insertion (SSAI), the server stitches ads into each viewer's manifest. With client-side ad insertion (CSAI), the player requests and plays ads itself. Break-based SGAI keeps server-side ad decisioning but moves the stitching to the device. Our SGAI vs. SSAI vs. CSAI comparison covers the trade-offs.

How does Google Ad Manager SGAI work?

Google describes its server-guided ad insertion as a solution that uses Pod Serving DAI to provide on-device stitching of Google-provided ad breaks. Those breaks can include ads from Google or third-party ad servers (Google documentation).

In Google's documented livestream flow, the client app registers a stream session with Ad Manager and polls for upcoming ad break metadata. When a break is due, the player loads an ad pod manifest and switches from the content manifest to the ad pod. A stream server can optionally insert ad markers into the content manifest to guide that schedule.

Google states that SGAI can be implemented on platforms with and without IMA SDK support, using the DAI Pod Serving API (livestream guide). Its IMA DAI SDK documentation includes SGAI guides with HLS Interstitials client-side scheduling for iOS and tvOS (iOS, tvOS).

When Google introduced SGAI for livestreams in April 2025, it cited squeezebacks and L-banners, where ads appear alongside continuously playing content. It also said SGAI is designed to work with HLS Interstitials and the then-upcoming DASH specification (Google Ads Developer Blog).

How do MediaTailor server-guided mode and HLS Interstitials work?

AWS Elemental MediaTailor offers a server-guided mode that references ads as separate playlists rather than stitching them into media playlists. AWS says this makes manifests cacheable and improves scalability (AWS documentation).

A MediaTailor playback configuration set to Player select lets each player choose stitched or guided insertion when the session starts. For HLS implicit sessions, the player adds aws.insertionMode=GUIDED to the multivariant playlist request. In November 2025, AWS added HLS Interstitials support for live streams. It named HLS.js, Shaka Player, Bitmovin Player, and Apple devices on iOS 16.4, iPadOS 16.4 and tvOS 16.4 or later as supported players (AWS announcement).

HLS Interstitials is the Apple-defined mechanism underneath much of this. A server places EXT-X-DATERANGE tags with the class "com.apple.hls.interstitial" in the playlist. Each tag points to an interstitial asset or an asset list. The player schedules that media on the content timeline, and devices without interstitial support ignore the tags (Apple specification guide).

MPEG-DASH has an equivalent. Alternative MPD events tell a DASH player to switch from the main presentation to an alternative MPD at set times. They are carried in the sixth edition of ISO/IEC 23009-1, which castlabs reported as published in August 2026 (castlabs).

What is StreamLayer SGAI?

StreamLayer SGAI combines server-side decisioning and orchestration with client-side rendering by the StreamLayer SDK inside the publisher's app. It adds ad units alongside the stream rather than switching the player to ad media.

StreamLayer does not stitch new video into the stream and does not modify the underlying video stream. Instead, it delivers three products:

• Moment Ads: live nonlinear ads activated around selected moments or lulls while programming continues, in formats such as Overlay, L-Bar, Side-Bar and PiP.
• Pause Ads: units that appear when a viewer pauses and close when playback resumes.
• Interactive SSAI: a synchronized interactive companion layer on video spots that the SSAI provider still stitches and delivers.

The platform has three parts. StreamLayer Studio handles campaigns, creative, pacing, eligibility, closing rules and reporting. Server services, including the Trigger Engine, make decisions. The SDK renders the units. The host app supplies signals such as pause events and timed metadata, and controls the player layout. See StreamLayer SGAI and how StreamLayer SGAI works.

Because decisioning is server-side and rendering happens on the device, each viewer can receive a different creative, offer or CTA. Live data, such as scores and stats, can also feed the units.

Are Google SGAI, MediaTailor SGAI and StreamLayer SGAI alternatives?

Mostly, no. Break-based SGAI changes how ad breaks are delivered. StreamLayer SGAI adds nonlinear, pause and interactive companion inventory. A publisher can use both.

A typical combined setup looks like this:

• Google Ad Manager or MediaTailor delivers ad breaks with server guidance and on-device stitching.
• StreamLayer renders Moment Ads during programming and Pause Ads when viewers pause.
• Where the stream carries timed metadata for a spot, StreamLayer adds an Interactive SSAI layer to it.

There is some overlap. Google cites squeezebacks and L-banners as SGAI use cases, and StreamLayer also offers L-Bar and Side-Bar layouts. The difference is what fills the space. Break-based SGAI plays ad media that the player switches to. StreamLayer renders interactive units with live data, QR codes, CTAs, polls and commerce, controlled by publisher rules.

Which kind of SGAI do you need?

Choose based on the problem you are solving. Many publishers will need both.

• Your problem is break delivery. If you want cacheable manifests, lower server load or client-side ad switching, evaluate Google Ad Manager SGAI or MediaTailor server-guided mode. Confirm HLS Interstitials or DASH Alternative MPD support in your players.
• Your problem is inventory growth. If you want revenue that does not add breaks, evaluate StreamLayer Moment Ads and Pause Ads.
• Your problem is spot engagement. If you want existing SSAI spots to carry QR codes, CTAs or live data, evaluate Interactive SSAI.
• Your problem is device reach. Check which of your players support interstitials or alternative MPDs, and which platforms the StreamLayer SDK supports at docs.streamlayer.io.

Frequently asked questions

What does SGAI stand for?

SGAI stands for server-guided ad insertion. Google, AWS and the streaming standards use it for ad breaks that the player stitches under server guidance. StreamLayer uses it for server-decided ads that its SDK renders alongside the stream.

Does StreamLayer SGAI replace Google Ad Manager or MediaTailor?

No. StreamLayer works alongside existing SSAI, CSAI, ad servers such as Google Ad Manager, SSPs, DSPs and players. It adds inventory and interactivity rather than replacing break delivery.

Do HLS Interstitials work on every device?

No. Apple's guide states that devices without HLS Interstitials support ignore the interstitial tags. Publishers should check support in each player they use.

Does StreamLayer SGAI modify the video stream?

No. StreamLayer does not stitch new video into the stream or modify it. The StreamLayer SDK renders units in the app while the stream plays.

If you are planning SGAI for breaks, for new inventory or for both, talk to StreamLayer about how the pieces fit in your stack.