Title, description, and a thumbnail image: if you get these three things right, people will pay attention to what you share on Facebook.
Once you publish a link via a page post, the Facebook Crawler will scrap the page’s URL, and pull what it sees as the title, description, and image.
If the page times out or is protected, the crawler won’t be able to get any information; you will be sharing a broken link.
You can easily test if the crawler has visibility on your page by running the following command:
curl -v --compressed -H "Range: bytes=0-524288" -H "Connection: close" -A "facebookexternalhit/1.1 (+http://www.facebook.com/externalhit_uatext.php)" "http://blog.leocelis.com/2019/06/12/facebook-ads-tools/"
(Replace the URL at the end, with your own.)
There are two other methods that you can use to validate if the crawler got your content right, and what properties you can update to make it more appealing: