The HTML5 specification introduced the video element for the purpose of playing videos, The following HTML5 code fragment will embed a WebM video into a web as shown below, the browser will choose automatically which file to download. does not specify which video and audio formats browsers should support.
If the browser supports WebM , it plays chrome.webm; if not, it checks whether the browser can select a video source without having to download part of the video to "sniff" the format.
