In-stream video ads play inside a video player, as part of a video content experience — pre-roll before a show, mid-roll during a match, post-roll after content ends. The viewer came to watch video content, and the ad appears within that viewing session. In-stream ads on CTV require the viewer to be actively streaming content. Out-stream video ads play outside a video player — in a web page article, between social feed cards, or in a standalone unit that autoplays as the viewer scrolls. Out-stream does not require surrounding video content.
On CTV, almost all advertising is in-stream. The CTV environment is a lean-back video viewing experience — the viewer opened a streaming app to watch content. Pre-roll, mid-roll, and post-roll are all in-stream. Home screen banner ads on Samsung Ads are not in-stream (they appear on the device home screen, not inside a video player) but they are also not out-stream in the traditional sense. True out-stream video on CTV is rare — it would require a browsing or reading interface on the TV screen, which is not how CTV is primarily used. When a DSP offers 'CTV out-stream', verify what inventory this actually represents — it is often lower-quality or misclassified inventory.
Full guide
For a complete explanation, read: In-stream vs out-stream video ads on CTV: definitions, differences, and what matters