This quick tip comes courtesy of Bob Dunn, aka BobWP.
In theory if you set up a featured image on your blog post or web page, Facebook (or Twitter, or other websites using open graph) should show that when someone shares your article. But if you forgot to add a featured image, or have changed your featured image, there’s a pretty good chance that Facebook is showing the wrong photo (or no photo) along with your link. If a Facebook share is showing the wrong image, here’s what to do:
Don’t let the name of the tool scare you, but you can use something called the Object Debugger – Facebook for Developers to help Facebook grab the right thing.
From that page, you can enter the URL to your page, view the information Facebook currently knows, and tell it to re-scrape the page to grab your current photo. That should pull in the most current information including the image that Facebook shows when you or someone else shares the article.
Thanks again to Bob for this tip for if you see the wrong image on a Facebook share.