title: How to validate youtube video ids?
body: <p>I want to validate youtube video ids sbumitted in the URL to one of my sites before accessing the Youtube API, but I don't know what the allowed characters are in such an id. I see people on the net guessing it can contain numbers and characters, but I haven't yet seen an official specification of these video ids.</p>
  
  <p>Is there one? </p>