This feature is accessible through the "Insert Media" dialog when posting a message. It adds two options (unchecked by default) that allows the user to look for embeddable URLs if the one they submit does not match any active media site. For example, if a user tries to submit
a t.co (Twitter's URL shortener) link to a YouTube video it will not be recognized by default, but if the user checks "Use the canonical URL" then it will be recognized as a YouTube...