Question

I’m playing with facebook links via posting them. On the frist time a access from a user agent containing “facebookexternalhit” will visit your site and look for some meta tags.

So far so good that works. But if I try to repost the link no furure calls happens. How can I trigger to let facebook read the page again?

Are there some API calls I can use to trigger an update?

Answer 1

in the documentation for the Like Button it says:

When does Facebook scrape my page?

Facebook needs to scrape your page to know how to display it around
the site.

Facebook scrapes your page every 24 hours to ensure the properties are
up to date. The page is also scraped when an admin for the Open Graph
page clicks the Like button and when the URL is entered into the
Facebook URL Linter. Facebook observes cache headers on your URLs – it
will look at “Expires” and “Cache-Control” in order of preference.
However, even if you specify a longer time, Facebook will scrape your
page every 24 hours.

The user agent of the scraper is: “facebookexternalhit/1.1
(+http://www.facebook.com/externalhit_uatext.php)”

The Linter is now known as the Facebook Debugger and when you use it for a url, it will clear the facebook cache for the same url and will then cache the new result.