>>105181If you are using a browser that supports webm then it will be using webm if it doesn't support it then it falls back to mp4. The wiki link I posted even states that.
>The default video stream is encoded in the VP9 format with stereo Opus audio; if VP9/WebM is not supported in the browser/device or the browser's user agent reports Windows XP, then H.264/MPEG-4 AVC video with stereo AAC audio is used instead. 
