I’m trying to have a share button on my site that can share on behalf of YouTube. Let’s say the page is http://www.mysite.com/test.html.
test.html
<!DOCTYPE html>
<html>
<head>
<meta property="og:url" content="http://www.youtube.com">
<meta property="og:description" content="My custom YouTube share">
<meta property="og:title" content="YouTube Share">
<meta property="og:image" content="http://www.mysite.com/preview.png">
</head>
<body>
<a href="http://www.facebook.com/sharer.php?u=http%3A%2F%2Fwww.mysite.com%2Ftest.html">Share</a
</body>
<html>
But it’s completely ignoring my meta properties when I click the Share. How can I get it so that Facebook looks at all of my declared meta properties? Or is it impossible to share on behalf of another site?
EDIT:
Here’s a sample screenshot of what I’m trying to do:

To get custom text on another site’s content share, you could use a URL on your site as the og:url, serve facebook’s crawler the meta tags with the title, description etc that you want, but redirect other browsers to YouTube
(i.e share a link to a URL on your site, then on that URL have logic which says
if user agent == Facebook’s crawler serve meta tags, else HTTP 301 redirect to youtube