Open Graph Tags are Meta-Data in the source-code of a website, containing information on the content of the website.
It can be various information, such as the title of an article, the preview image to be used, the author, a brief summary of the content, etc.
In case these tags are not set correctly on a website, swat.io may return unwanted results when loading the preview or may not be able to display the preview at all. In that case an error message is displayed with a reference to the incorrect Open Graph Tag.
If this involves a link to a website to which you have full control, you can bring it to the attention of the web team to correct the errors in the site's Open Graph Tags. The Facebook Sharing Debugger will help you doing this. After that, you can try adding the link again and creating the link preview should display the desired results.
If you want to share a link to a website for which you do not have control, you can of course still post the link on Facebook. In case no preview image is specified in the website's Open Graph Tags or the Open Graph Tags are just set incorrectly, Facebook will create the link preview according to its own ideas. As a consequence Facebook will "guess" the correct preview image.
You can test this process to some extent beforehand by entering the link you want to post in Facebook's sharing debugger and by clicking on "Debug". It will then display a list of the Open Graph Tags included in article, as well as any issues with these. You will also receive a preview of how the link-preview on Facebook will probably look like after posting it on Facebook:
Of course, it is best to always set the correct Open Graph Tags on your own web pages, blogs, etc., because not only Facebook, also other social media and search engines rely on that kind of metadata. Correctly set Open Graph Tags will therefore increase the chances of your content being seen in the world wide web drastically.
If you have any further questions, don't hesitate to contact our support team either via chat or via email@example.com!