This is not a common problem. Because when I paste a YouTube URL into a comment on card in Trello, sometimes it just ends with an embedded YouTube video which is just what I want, however, sometimes it won't work. The comment will show a plain hyperlink as I pasted in which is not good. How to solve this problem?
1 Answer
Trello uses embed.ly to generate previews for certain types of links, including links to youtube.
If you go to embed.ly, you can test it with that URL (http://www.youtube.com/twitterapi#p/u/7/HY5GIl7sFwE), and see that it isn't able to get a proper preview (because the link isn't in a format that it recognizes)
However, if you use a link like http://www.youtube.com/watch?v=HY5GIl7sFwE (which points to the same video), that is in a format that embed.ly recognizes, so Trello is able to get the preview.