Facebook uses og:tags
and the Open Graph Protocol to decipher what information to display when previewing your URL in a share dialog
or in a news feed on facebook.
The og:tags
contain information such as :
- The title of the page
- The type of page
- The URL
- The websites name
- A description of the page
- Facebook user_id's of administrators of the page ( on facebook )
Here is an example ( taken from the facebook documentation ) of some og:tags
<meta property="og:title" content="The Rock"/>
<meta property="og:type" content="movie"/>
<meta property="og:url" content="http://www.imdb.com/title/tt0117500/"/>
<meta property="og:image" content="http://ia.media-imdb.com/rock.jpg"/>
Once you have implemented the correct markup of the og:tags
and set their values, you can test how facebook will view your URL by using the Facebook Debugger. The debugger tool will also highlight any problems it finds with the og:tags
on the page or lack there-of.
One thing to keep in mind is that facebook does do some caching with regard to this information, so in order for changes to take effect your page will have t be scraped as stated in the documentation :
Editing Meta Tags
You can update the attributes of your page by updating your page's
tags. Note that og:title and og:type are only editable
initially - after your page receives 50 likes the title becomes fixed,
and after your page receives 10,000 likes the type becomes fixed.
These properties are fixed to avoid surprising users who have liked
the page already. Changing the title or type tags after these limits
are reached does nothing, your page retains the original title and
type.
For the changes to be reflected on Facebook, you must force your page
to be scraped. The page is scraped when an admin for the page clicks
the Like button or when the URL is entered into the Facebook URL
Linter Facebook Debugger...