Glossary
What is SSAI (server-side ad insertion)?
Also called: server-side ad insertion, ad stitching, DAI
SSAI (server-side ad insertion) stitches video ads into the content stream on a server, so the viewer's device plays one continuous stream.
हिंदी में पढ़ेंWith client-side ad insertion, CSAI, the player pauses the show, calls the ad server, reads the VAST, downloads the video and plays it. On a slow TV or network, that can mean a spinner mid-break. With SSAI, a stitching server requests the ad for each viewer, picks a ready, transcoded copy and splices it into the video segments. The device plays one smooth stream, like broadcast TV.
The catch is measurement. Thousands of impressions now report from one server, which can look like invalid traffic. So VAST says stitching providers must pass each viewer’s details in the X-Device-IP and X-Device-User-Agent headers; the older X-Forwarded-For header is deprecated.
Google’s Dynamic Ad Insertion is one server-side service. Newer hybrids exist too, such as server-guided ad insertion, which does the stitching on the device. SSAI is common in CTV, where ads play in pods like TV commercial breaks.
Example
10,000 viewers reach one mid-roll. With CSAI, 10,000 devices each make their own ad call. With SSAI, the stitching server makes the 10,000 requests, one per viewer, and must forward 10,000 sets of device IP and user agent so buyers can tell the viewers apart.
Why it matters to publishers
SSAI makes ad breaks smoother, but missing device headers can make real viewers look like invalid traffic and cost bids. Ask any SSAI vendor whether its requests and tracking calls pass them.