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. WebM was originally designed to be used on webpages to save bandwidth, but it also has some benefits when it comes to video games and many other applications.

The biggest benefit of WebM over Bink (or AVI) is that of file size; a WebM video will be significantly smaller than that of a similar-quality Bink file, without dropping video quality. For example, the installation size of Hunt Down the Freeman decreased by 5.7 GB when switching its FMV cutscenes from Bink to WebM^[1]. Furthermore, unlike Bink, WebM is much more common and easier to make than Bink file format, as Bink requires a tool that only takes AVI and other format (MP4 requires deprecated QuickTime for Windows application) and converting it to Bink, then only to find out there's audio or video sync issues that may sometimes happen.

WebM is supported in the following games, engines, and engine branches:

• Source 2
• Strata Source
• Counter-Strike: Global Offensive (since 2018 Panorama update)
• Hunt Down the Freeman

References

1. Hunt Down The Freeman - July blog: where we're at + looking for team members! - Steam News
   Bink video is replaced with webm (like CSGO and Source 2) and has successfully freed up 5.7GB of space