At a minimum, every page should include these four properties to ensure a professional preview: The Open Graph protocol
In the context of web development, og is the standard prefix for the . It is a semantic namespace that signals search engines and social platforms: "The properties that follow belong to the Open Graph specification." og https ogp.me ns
While modern browsers and social crawlers are increasingly flexible, the official specification suggests declaring the namespace in one of two ways: At a minimum, every page should include these
<html prefix="og: http://ogp.me/ns#">
| Problem | Likely Cause | Fix | |---------|--------------|-----| | Facebook shows old image | Cache | Use the Facebook Sharing Debugger to scrape again. | | LinkedIn ignores og:description | Missing og:type | Ensure <meta property="og:type" content="article"> is present. | | Slack shows raw URL, no preview | Missing og:title | Add at minimum og:title and og:image . | | W3C Validator complains about xmlns:og | Using XHTML doctype without namespace | Add xmlns:og="https://ogp.me/ns#" to <html> or switch to HTML5. | | | Slack shows raw URL, no preview
The feature you are referring to is the Open Graph Protocol (OGP) , which is defined by the namespace declaration prefix="og: https://ogp.me"