Open Graph & Link Preview Glossary
Quick reference for every term you will encounter when working with Open Graph tags, link previews, and social sharing. Designed for developers, marketers, and WordPress beginners alike.
This glossary covers 31 terms alphabetically. Click any term in the list below to jump directly to its definition, or scroll through the full glossary.
Absolute URL
A complete URL including protocol and domain (e.g., https://example.com/image.jpg). All OG tag values that reference URLs must be absolute. Relative URLs like /image.jpg will not work because crawlers need the full path to fetch the resource.
Aspect Ratio
The proportional relationship between an image's width and height. The recommended aspect ratio for OG images is 1.91:1, meaning the width is nearly twice the height. The most common dimensions are 1200×630 pixels. Using a different ratio may cause platforms to crop your image unpredictably.
Cache / Caching
Social platforms store (cache) a copy of your OG data after the first time someone shares your URL. This means updating your OG tags does not immediately change existing previews. To clear the cache, use each platform's debugger tool to force a re-scrape. See also: Sharing Debugger, Post Inspector.
Canonical URL
The preferred version of a page's URL, specified with a <link rel="canonical"> tag or the og:url property. When multiple URLs serve the same content (e.g., with and without trailing slash, with tracking parameters), the canonical URL tells platforms and search engines which one to treat as authoritative.
Card (Twitter Card)
A structured preview format used by Twitter/X when a link is shared. Twitter Cards come in several types, with summary (small image) and summary_large_image (large image) being the most common. Card behavior is controlled by twitter: meta tags in the page's <head>. See also: summary_large_image, Twitter Card.
Client-Side Rendering (CSR)
A technique where page content is generated by JavaScript running in the browser rather than being present in the initial HTML. Most social media crawlers do not execute JavaScript, so OG tags embedded by client-side frameworks (React, Vue, Angular) will not be detected. Pages using CSR typically need server-side rendering or a pre-rendering solution for OG tags to work.
Crawler / Scraper / Bot
An automated program that fetches web pages to read their content. Social platforms use crawlers to extract OG tags when someone shares a URL. These crawlers typically read only the raw HTML and do not execute JavaScript. Each platform's crawler identifies itself with a specific User Agent string.
Debugger
A tool that fetches a URL and displays the OG tags it finds, often with a preview of how the link will appear when shared. Debuggers are essential for troubleshooting broken or missing link previews. See: Sharing Debugger, Post Inspector, and the best OG preview tools roundup.
Fallback
When a platform-specific tag (e.g., twitter:title) is not present, the platform falls back to the equivalent OG tag (og:title). Twitter/X, LinkedIn, and most messaging apps support this fallback behavior. Defining a base set of og: tags ensures reasonable previews even on platforms you did not explicitly target.
Head Section (<head>)
The part of an HTML document between <head> and </head> that contains metadata, including OG tags. This section is not visible on the page itself but is read by browsers, search engines, and social media crawlers. All <meta property="og:..."> tags must be placed here.
Link Preview
The visual card (title, description, image) that appears when a URL is shared on social media or in a messaging app. Link previews are generated from the page's OG tags and, in some cases, Twitter Card tags. Different platforms render link previews differently, which is why multi-platform preview tools are useful.
Meta Tag
An HTML element in the <head> section that provides metadata about a page. OG data is stored in meta tags using the property attribute (e.g., <meta property="og:title" content="My Page">). Twitter Card data uses the name attribute (e.g., <meta name="twitter:card" content="summary_large_image">).
Namespace
A prefix that groups related attributes to avoid naming conflicts. Open Graph uses the og: namespace (e.g., og:title, og:image). Twitter uses the twitter: namespace. The og: namespace is formally defined in the Open Graph protocol and was originally tied to RDFa.
og:description
The OG tag that provides a brief summary of the page's content. Most platforms display 1–2 sentences. Recommended length is 60–200 characters. If omitted, platforms may pull text from the page body or the <meta name="description"> tag, often with poor results.
og:image
The OG tag that specifies the image shown in link previews. The value must be an absolute URL. Recommended dimensions are 1200×630 pixels (1.91:1 aspect ratio). This is arguably the most important OG tag because a missing or broken image drastically reduces engagement with shared links.
og:title
The OG tag that sets the title shown in link previews. Keep it under 60 characters to avoid truncation on most platforms. If omitted, platforms fall back to the <title> element, which may include site name suffixes or other text not ideal for social previews.
og:type
The OG tag that describes the type of content. Common values are website (default for most pages), article (for blog posts and news), and profile. Most social platforms do not visibly change the preview based on this value, but it is part of the protocol specification and should be included.
og:url
The OG tag that defines the canonical URL for the page. When set, all shares of the page are attributed to this URL regardless of the actual URL that was shared. This consolidates share counts and ensures consistent preview data.
Open Graph (OG)
A protocol that allows web pages to control how they appear when shared on social media and messaging platforms. OG tags are HTML meta tags placed in a page's <head> section. Originally created by Facebook in 2010, the protocol is now supported by virtually all platforms that display link previews.
Open Graph Protocol
The formal specification that defines the og: meta tags and their expected values. The protocol is documented at ogp.me. It defines basic tags (og:title, og:type, og:image, og:url) and optional tags (og:description, og:locale, etc.) along with rules for structured properties.
Post Inspector (LinkedIn)
LinkedIn's official tool for previewing and refreshing link previews. Paste a URL to see how it will appear when shared on LinkedIn, and force LinkedIn to re-scrape the page to pick up updated OG tags. Requires a LinkedIn account.
RDFa
Resource Description Framework in Attributes — a W3C standard for embedding structured data in HTML. Open Graph tags are technically an application of RDFa, using the property attribute on meta tags (as opposed to name). In practice, you do not need to understand RDFa to use OG tags correctly.
Robots.txt
A text file at the root of a website (/robots.txt) that tells crawlers which pages they are allowed or disallowed from accessing. If your robots.txt blocks a social media crawler, that platform will not be able to read your OG tags and will not generate link previews. Ensure social media bot user agents are not blocked.
Schema Markup / JSON-LD
A structured data format (usually embedded as <script type="application/ld+json">) that helps search engines understand page content. Schema markup and OG tags serve different purposes: Schema is for search engine rich results, while OG is for social media link previews. A well-optimized page typically includes both.
Scrape / Re-scrape
The act of a crawler fetching a URL to read its OG tags. A re-scrape forces the platform to fetch fresh data, clearing its cache. You can trigger a re-scrape using official debugger tools (Facebook Sharing Debugger, LinkedIn Post Inspector) or tools like PreviewOG.
Server-Side Rendering (SSR)
A technique where the server generates complete HTML (including OG tags) before sending it to the browser. SSR ensures that social media crawlers — which do not execute JavaScript — can read your OG tags. If your site uses client-side rendering, you need SSR or pre-rendering for OG tags to work correctly.
Sharing Debugger (Facebook)
Facebook's official tool for previewing and refreshing link previews. Enter a URL to see exactly how Facebook will render it, view any warnings, and force a re-scrape to clear cached data. Requires a Facebook account.
Structured Properties
OG tags that use dot notation to define sub-properties of a parent tag. For example, og:image can have structured properties like og:image:width, og:image:height, og:image:type, and og:image:alt. Providing structured properties helps platforms render previews more accurately without having to download and analyze the image.
summary_large_image
A Twitter Card type that displays a large image above the title and description. This is the most common card type for articles and blog posts. Set it with <meta name="twitter:card" content="summary_large_image">. The summary type uses a smaller square image to the left of the text.
Twitter Card
A set of meta tags (using the twitter: prefix) that control how links appear on Twitter/X. The most common tags are twitter:card (card type), twitter:title, twitter:description, and twitter:image. When these tags are absent, Twitter/X falls back to the equivalent og: tags. See also: Card, summary_large_image.
User Agent
A string sent by a browser or crawler that identifies itself to the web server. Social media crawlers use specific user agent strings (e.g., facebookexternalhit for Facebook, Twitterbot for Twitter/X, LinkedInBot for LinkedIn). Knowing these strings is useful for debugging when a platform cannot read your OG tags — it may be blocked at the server or CDN level.
Social Share Preview
Another name for a link preview. The card that appears when a URL is posted on a social network or messaging app, typically showing a title, description, and image pulled from the page's OG tags.