CSAI vs SSAI: Client-Side vs Server-Side Ad Insertion
There are two main ways to put ads into a video stream: the player does it (client-side ad insertion, CSAI) or the server does it before the stream reaches the player (server-side ad insertion, SSAI). Both depend on knowing where the breaks are.
Client-side ad insertion (CSAI)
The player plays the program. When it reaches a break, it pauses the program, requests an ad from an ad server (commonly through VAST), plays the ad and returns to the program.
- Strengths: simpler to set up for web and app players you control; rich interactive ad formats; detailed player-side measurement.
- Limits: the switch between program and ad can show buffering; ad blockers can stop the ad request; behavior varies between devices.
Server-side ad insertion (SSAI)
A server stitches the ads into the stream itself. The player receives one continuous stream with the ads already inside.
- Strengths: smooth, TV-like playback; works on connected TVs and devices with simple players; harder to block.
- Limits: more infrastructure in the delivery chain; measurement needs to be reported from the server or with player support.
How to choose
- Your own web and app players: CSAI is often the faster start.
- Connected TV, FAST and third-party platforms: SSAI is the common model, and the platform often runs it.
- Many destinations: you may use both, one per distribution target.
What both need
Accurate break markers. SCTE-35 cues tell the player or the server where a break starts and how long it lasts. If the markers are missing or wrong, neither model can place ads correctly.
Fast Monkey Pass preserves SCTE-35 markers from your feed and supports client-side or server-side ad insertion workflows, depending on each distribution target. Fast Monkey One places the markers in playout.