In-stream video ads are placed within the context of other video content, for example on YouTube. These ads generally cannot be skipped. If users want to watch a video, they are essentially required to watch the ad as well. There are three ways to integrate in-stream video ads:
Pre-roll videos are played before the actual video.
Mid-roll video ads interrupt the video.
Post-roll video ads play after the video. Attention is usually quite low at this point, as users have already seen the content they wanted and can skip the ad by clicking to the next video.