CTV & video
Instream video
Instream video is a video ad that plays within a video player before, during or after video content the viewer chose to watch, such as pre-roll, mid-roll or post-roll.
Instream ads run inside the video experience: you choose a video, and ads play at the start (Pre-roll), during (Mid-roll) or at the end (post-roll). The ad takes over the player that would otherwise show content.
Because viewers actively chose to watch and usually have sound on, instream is considered premium video inventory, with higher viewability, completion rates and prices than outstream video. On CTV, nearly all ads are instream.
IAB Tech Lab tightened the definition in 2023. Under the updated OpenRTB "plcmt" field, instream means ads played in video content the user requested, with sound on by default or where the user expects audio. Players that auto-play muted content alongside articles are "accompanying content", not instream. The change aimed to stop sellers mislabelling lower-value placements as instream. Buyers can check this signal and verify it with measurement.
Think of it like this
Instream video is like the adverts during a TV show you sat down to watch, rather than posters on the wall of the room.
An example
A buyer targeting only instream placements in the UK filters bid requests to plcmt=1, then compares performance with its "accompanying content" buys: completion is 88% versus 51%.
Related terms
Outstream video
Outstream video is a video ad that plays outside of video content, for example within an article, a social feed or between paragraphs, usually auto-playing muted as it scrolls into view.
Pre-roll
Pre-roll is a video ad that plays before the content the viewer chose to watch begins.
Mid-roll
Mid-roll is a video ad or ad break that plays partway through content, interrupting it, like a traditional TV commercial break.
VAST
VAST (Video Ad Serving Template) is the IAB Tech Lab standard XML format that tells a video player which ad to play, where to fetch it and which tracking events to report.
OpenRTB
OpenRTB is the open technical standard, maintained by IAB Tech Lab, that defines how bid requests and bid responses are formatted and exchanged in real-time bidding.
Sources: IAB Tech Lab OpenRTB, IAB Tech Lab VAST