Manage your social media preview images and search engine results display from this easy to use front end Joomla extension, 4SEO.
Prepare your "hero" preview image to the size of 1200 x 630 pixels with some room around the edges to allow for cropping by the different social media platforms.
Facebook debugger (login to your account first) :https://developers.facebook.com/tools/debug/
Twitter debugger (login to your account first) I have noticed thsi is not really an acurate preview.:https://cards-dev.twitter.com/validator