It is a rather complex topic though, due to the variety of formats, codecs, containers and combination of operating systems and browsers. We therefore generally recommend to only embed video in the .mp4 format in single pages. MP4 is the mandatory file format for creating a video learning resource.
The mp4 container using the H.264 video codec and the mp3 audio codec is widely established and accepted. Current Firefox, Chrome and Safari are capable of playing videos encoded in such a way.
In OpenOLAT videos can be implemented in different ways: