Facebook's expansion of links in comments on Pages not deterministic?

Question

When adding comments that contain embedded URL links to posts on Pages, it seems that Facebook sometimes expands these links (i.e., displays an associated Preview of the link), and sometimes does not.

Is there any underlying logic that deterministically governs when links are or are not expanded?

I've not yet succeeded in finding any fixed patterns, despite experimenting with such factors as:

• whether or not I have Admin rights to the specific Page in question.
• on Pages for which I do have Admin rights, which "voice" I am using when making the comment. I.e., whether I "use Facebook" (or perform "posting, commenting, and liking") either "as that Page" or "as myself".
• whether I explicitly include the URI Scheme in the URL or not; and if so, whether I use "http://" or (if relevant) "https://".
• which web-browser I use when posting the comment: Chrome or Firefox.

For all combinations of these factors that I've tried, sometimes the link in the comment gets expanded, and sometimes it does not.

And in those cases where the link does not get expanded, I've tried refreshing (and even completely restarting) the browser -- an action that I have sometimes found helpful with other Facebook-related problems, but not with this particular problem.

Answer 1

Maybe it was different in the past, but now I can reproduce it quite well.

Step 1: Post your message with only one link in it.
Step 2: Make sure you hit enter in the comment box after you type the URL (e.g. URL can be on one line). Even if you do not wan to add any more text just hit enter and then Facebook will expand your link.

If you do by mistake Step 3: Delete the preview or delete the link in your post and you type a new link in your post it won't be expanded anymore, you will have to forget about that comment, preferably refresh your page and start posting again.

If you have any problems with the link not displaying the preview or the preview being old, be aware that facebook caches these preview information and you need to go the facebook developer tool at: https://www.facebook.com/login.php?next=https%3A%2F%2Fdevelopers.facebook.com%2Ftools%2Fdebug%2F

There you can ask facebook to go one more time and read one more time the information from your URL and refresh the facebook cache with newer information by clicking on the button "Scrape Again"

You can also see the warnings or errors your URL is generating while being fetched by Facebook. If your page does not display at all still while posting and following Step 1 and 2 above, you might want to fix the errors identified by the Facebook developer tool.