Server-Side Ad Insertion (SSAI)

Server-Side Ad Insertion (SSAI) is a streaming advertising technique that stitches ads into video content on the server or CDN edge so viewers receive a single, continuous media stream rather than separate ad and content requests. SSAI uses manifest manipulation and ad decisioning (for example SCTE-35 cues and VAST responses) to enable seamless playback, reduce ad-blocking, and support personalized and programmatic ads across OTT, CTV, mobile and web environments.

Think of it like a tailor sewing ad patches into a garment before it reaches the customer: the server stitches ad assets into the content stream using SCTE-35 markers and ad decision responses so the player just plays one smooth file. An ad decision server or SSP evaluates targeting and inventory, returns VAST/CMAF segments, and a CDN-edge SSAI component composes the final HLS/DASH manifest delivered to the client. You’ll find measurement, verification and tracking implemented via a mix of server logs and client beacons, which trades some client-level signal for greater ad-blocker resilience and smoother playback. Header-bidding-style server auctions and prefetching of ad pods are increasingly common to maximize yield and reduce latency.

Publishers and broadcasters running OTT apps and CTV channels are the primary adopters of SSAI, seeking improved viewer experience and lower ad-block loss, while SSAI vendors and CDNs supply the stitching technology and operational services. Advertisers, DSPs and agencies buy stitched inventory programmatically or via direct deals, typically paying CPMs or programmatic guaranteed rates, with SSPs and ad servers brokering supply. Measurement providers, verification firms and identity vendors influence pricing and targeting capabilities, and privacy regulations (GDPR, CCPA) plus industry ID solutions shape how personalization and signal sharing work. Smaller publishers often use managed SSAI platforms or SSP bundles, while large broadcasters may build custom, in-house SSAI stacks integrated with their ad-ops systems.