Definition
In-stream means inside the stream of content the visitor is watching, as opposed to out-stream units that play in an article or a feed. The player pauses the content, plays the ad, and resumes. The IAB's Video Ad Serving Template (VAST) is the XML format that tells the player where the video file is, how long it runs, when it may be skipped and which tracking pixels to fire at start, first quartile, midpoint, third quartile and completion.
How in-stream video ads work
- The publisher's player requests an ad from the network with the visitor's GEO, device and the slot position (pre, mid, post).
- The network auctions the slot among video campaigns and returns a VAST tag for the winner.
- The player loads the MP4 and plays it; quartile pixels report how much was watched.
- The advertiser is charged per thousand starts (CPM) or per completed view (CPV), depending on the deal.
Creative requirements
An MP4 of up to 30 seconds in 16:9 for desktop and horizontal players and 9:16 for vertical mobile players, within the network's file-size cap (20 MB on Reacheffect), or an existing VAST tag from the advertiser's own ad server. Fifteen seconds is the common length because skip controls appear at five or six seconds and completion rates fall after fifteen.
Who uses in-stream video
Advertisers with a story to tell before the click: iGaming brands, sportsbooks around live events, sweepstakes, dating apps and streaming services promoting their own catalogues. Publishers of streaming, sports highlights and short video supply the inventory.
Related terms
| Term | Relation | Where defined |
|---|---|---|
| Interstitial ads | Full-screen alternative without a player | Term page |
| CPM | Pricing model | Term page |
| Real-time bidding | How video is traded between platforms | Term page |
| Ad server | Where VAST tags come from | Term page |
FAQ
What is VAST?
Video Ad Serving Template, the IAB's XML standard that lets any compliant video player fetch and play an ad from any ad server and report how much of it was watched.
Is in-stream video CPM or CPV?
Both exist. CPM charges per thousand ad starts; CPV charges per completed view, usually defined as the full ad or 30 seconds, whichever comes first.
How long should a video ad be?
Fifteen seconds for most campaigns; up to 30 seconds is accepted. Put the brand and the offer in the first five seconds, before any skip control appears.