CSAI (client-side ad insertion)
CSAI (client-side ad insertion) is a method where the video player itself requests and plays ads, pausing the main content to show them. The player fetches ad details, usually through a VAST or VMAP tag, then loads and plays the ad file before returning to the show. Ads and content come from separate sources.
Why it matters
CSAI is the quickest way to add ads to a video app and supports clickable, measurable formats advertisers like. The cost is lost revenue from ad blockers and a jarring pause while ads load, which can push viewers away on slow connections.
How it works
- The player reaches an ad break, often set by a VMAP schedule.
- It requests an ad from the ad server using a VAST tag.
- The ad server returns the ad file location and tracking links.
- The player pauses the content, plays the ad and sends tracking events.
- When the ad finishes, the player resumes the main video.
What are the disadvantages of client-side ad insertion?
The main disadvantages of client-side ad insertion are ad blocking, buffering between content and ads, and uneven support across devices. Because the player fetches ads separately, blockers can stop the requests. Switching sources can cause a pause, and some smart TVs handle CSAI poorly.
Is CSAI or SSAI better for mobile apps?
CSAI often works well for mobile apps because ad blocking inside apps is rare and clickable ads perform well on touch screens. SSAI may still be better for long live streams in apps, where smooth breaks matter more than clicks. Many apps choose by content type.
Where it's used
Web and mobile video apps, including OTT services, microdrama apps and creator platforms, use CSAI for clickable ads and detailed tracking, accepting that ad blockers can stop some ads.
