title: How does video on demand work in Youtube?
body: <p>I am trying to understand how Video On Demand works on Youtube. I found out that my browser is downloading many WebM files. When I download one of the WebM video chunk and try to play it on Chrome it does not play.</p>
  
  <p>Can you explain how WebM works with youtube? I read that there needs to be initialization and clusters. What is the file extension for the initialization file for WebM videos? Does cluster refer to many .webm files?</p>
  
  <p>From my basic understanding,</p>
  
  <p>Click on a youtube video -> Youtube sends initialization file -> Once browser downloads and accepts the file, the browser request 1st chunk .webm video file and play it -> request the second chunk.</p>
  
  <p>Is this correct?</p>