What is Server-Side Ad Insertion?
Server-side ad insertion (SSAI) places advertisements into a media stream or manifest before delivery. Ads and primary content can therefore play as a more continuous stream from the viewer’s perspective.
How Server-Side Ad Insertion works
An SSAI system selects an advertisement, prepares media compatible with the program, and rewrites manifests or constructs a stitched stream for a particular playback session. Markers in live or on-demand content define opportunities and timing, while tracking services reconcile requested, started, and completed impressions. Because the player consumes normal media segments, ad delivery is less dependent on client execution than a separate overlay. The system sits between origin packaging, ad decisioning, CDN delivery, and playback analytics.
Key facts
- Ad segments must align with the surrounding rendition’s codec, resolution constraints, timestamps, and segment boundaries; discontinuity signaling may be needed when properties change.
- Personalized manifest URLs can fragment CDN caches because viewers receive different segment sequences, so cache-key design and shared media objects materially affect efficiency.
- Client-visible media continuity does not eliminate measurement complexity: server logs, player beacons, seeking behavior, and ad-decision records can report different events.
When Server-Side Ad Insertion matters
Choose SSAI for personalized ads or live events where client-side transitions would disrupt playback. Ad stitching must preserve codec and timeline compatibility, or players may stall at content boundaries.