SSAI (server-side ad insertion), also called ad stitching, splices ads into the video stream at the server or edge, so the ads arrive as part of the same stream as the content. To the player, ad and content segments look identical — same format, same manifest timeline — which is exactly why SSAI resists ad-blockers and plays seamlessly, with no buffering at the ad boundary, on devices like smart TVs where client-side ad SDKs are weak.
The flow ties together several standards: SCTE-35 markers in the stream signal where an ad break may go; an ad decisioning service is called (speaking VAST/VMAP) to choose ads, often personalized per viewer; and the stitcher assembles a per-session manifest that weaves the chosen ads into the content. Because each viewer can get different ads, SSAI can fragment the CDN cache, so cache design and the split between shared content and per-user ads matter.
SSAI is the backbone of serious AVOD and FAST monetization; its trade-offs versus CSAI are seamlessness and block-resistance (SSAI) against simpler implementation and richer interactivity (CSAI).
The handbook · 7 volumes
Fora Soft Video Engineering Handbook
SSAI stitches ads into the stream so ad blockers cannot tell them apart, but stitching, ad tracking, and per-viewer manifests add server load. We wrote seven volumes covering the video stack; for SSAI start with Volume 3 on players and streaming economics, then Volume 2 on manifests, SCTE-35 cues, and packaging, with encoding in Volume 1. Written by Nikolay Sapunov, CEO at Fora Soft.
Moving to SSAI so ads play on every device and survive ad blockers?
We will review your packaging and ad stack and send an SSAI plan with vendor options and the cost per stream. 250+ video products shipped since 2005.
