Open Graph
Open Graph is a set of meta tags, each carrying a property name that starts with og:, placed in the head of a page to tell a platform how to present the page when someone shares a link to it: its title, a description, a preview image, its canonical URL and its type. It was introduced by Facebook and is read by most social networks and messaging apps.
The tags
The core set is small. og:title is the headline the card shows. og:description is the sentence under it. og:image is the preview picture, usually the tag that decides whether a share looks finished or broken. og:url is the canonical address the platform should count shares against, so that a page reached under several URLs collects one total. og:type says what kind of thing the page is, such as an article or a website, and og:site_name names the publisher. Every page on this site carries them; the head of this one is an example.
What it does not replace
The Open Graph title is not the title tag, and the Open Graph description is not the meta description. They are read by different programs for different purposes, and they can legitimately differ: a share card can afford a more inviting line than a search snippet. What they should not do is disagree about facts. An assistant that fetches a page receives all of them, and a page whose title tag, meta description and og:description give three different accounts of what it is has told a machine three things. Some platforms also read a parallel set of twitter: tags and fall back to Open Graph when those are absent; a page that sets both should keep them in step.
A question worth settling
Does Open Graph affect search ranking?
Google’s published list of the meta tags it acts on does not include any Open Graph property, so there is no documented ranking effect. What the tags change is the share card: whether a link to the page arrives in a feed or a chat with a title, an image and a sentence, or as a bare URL. That affects whether people click, and clicks are where any downstream effect would come from.
Related terms
Sources
Which meta tags Google acts on: Google’s list of the meta tags it supports. The Open Graph property names are described from this site’s own pages, which carry them.