It’s great that it worked for you (at least once).
– If you refer to format videos are recorded, Safari records mp4 and other browsers record webm . That is browser dependent. The webm videos can be converted to mp4 server side with VideoShareVOD plugin if you have FFmpeg on web hosting.
https://www.ads-software.com/plugins/video-share-vod/
– HTML5 is highly dependent on browser implementation and updates. If you encounter issues with a specific browser like Firefox, you can use Chrome, Brave, Edge until that gets updated.