WebM

WebM (.webm) is a video file format developed by  Google. It is subset of the  Matroska container format developed by  Xiph, and incorporates VP8 encoding technology by  On2. It is mainly used to display video and audio on the web browser, but it is also used on video games and it's engine, such as: Counter-Strike: Global Offensive (a Source game), all Source 2 games and aswell as Strata Source, all of these replaced the older Bink videos which was commonly used in Source and other third-party engines.