Server-side ad insertion (SSAI) is the technology that stitches ads into a video stream on the server before the stream reaches the viewer's device — as opposed to client-side ad insertion (CSAI), where the device loads the ad separately from the content. With SSAI, the video the CTV device receives is a single continuous stream with ads already embedded, making it technically identical to the content stream. This has three important consequences: (1) Ad blockers cannot detect or block the ad because there is no separate ad call from the device; (2) Buffering during ad transitions is eliminated — the stream plays continuously without the loading pause common with client-side ad breaks; (3) The ad is indistinguishable from content at the device level, which some publishers argue improves ad experience.
For India CTV, SSAI is the standard ad delivery mechanism for all major OTT publishers — JioCinema, JioHotstar, SonyLIV, and Zee5 all use SSAI for their ad-supported streams. This is why CTV ads on these platforms generally buffer less than mobile video ads and why ad blockers do not work on CTV as they do on desktop. The leading SSAI providers used in India include SpringServe (Magnite), Google DAI (Dynamic Ad Insertion), and AWS Elemental MediaTailor. For advertisers, SSAI is mostly invisible — it is the publisher's infrastructure choice. But understanding SSAI explains why CTV ad measurement requires the publisher's SSAI system to fire tracking beacons, rather than the advertiser's own ad tag firing independently as it would in a display campaign.
Full guide
For a complete explanation, read: Server-side ad insertion (SSAI) for CTV: how it works, why publishers use it, and what it means for advertisers