ryanve

Social media sites often use the image_src microformat for displaying link thumbnails. This simple plugin adds the image_src <a href="http://microformats.org/wiki/existing-rel-values" rel="nofollow ugc">rel value</a> to the code of your site. By default, the plugin applies only to singular views and it uses the <a href="https://codex.wordpress.org/Post_Thumbnails" rel="nofollow ugc">featured image</a>. It only applies when an image is available. The <code>'@image_src'</code> filter hook allows for image customization and/or extending the plugin to other views.

image_src

aitor.delapuente

This plugin helps ensure your content has a relevant thumbnail when shared on social sites.
Adds an image_src and og:image meta tags to your header using post thumbnnail (you must have post thumbnails / featured image enabled), first image on post/page content, or a defined default image.

FetenWeb image_src Metatag

This plugin helps ensure your content has a relevant thumbnail when shared on social sites.

image_src vs FetenWeb image_src Metatag