Reference
Open Graph & social image glossary
Every term you'll run into while making a link preview look right — defined in plain English, with the practical detail that actually matters.
- Open Graph (OG)
- A protocol, originally created by Facebook, that lets any page describe how it should appear when shared — via og: meta tags. Nearly every platform (LinkedIn, Slack, Discord, iMessage, WhatsApp) reads these same tags, which is why one set of tags works almost everywhere.
og:image- The meta tag whose value is the URL of the picture shown in a link preview. It's the single most important tag for how a shared link looks, and it must be an absolute https:// URL.
og:title / og:description- The headline and supporting line of the card. Keep the title under ~60 characters and the description under ~110 so neither gets truncated.
og:url- The canonical URL of the page being shared. Helps platforms de-duplicate and attribute shares to the right page.
og:type- Describes the kind of object being shared — 'website' for most pages, 'article' for blog posts and news (which unlocks extra tags like article:published_time).
twitter:card- An X (Twitter) specific tag that selects the card layout. summary_large_image requests the big landscape image card; without it, X may show a small thumbnail.
summary_large_image- The twitter:card value that produces a large, full-width image card on X — the layout most brands want for shared links.
- 1200×630 / 1.91:1
- The standard Open Graph image size in pixels and its aspect ratio. Design at 1200×630 and the same image fills the large card on Facebook, LinkedIn, Slack, and Discord.
- 2× export
- Rendering an image at twice its logical dimensions (so 1200×630 becomes 2400×1260) so it stays crisp on high-density 'retina' displays. FreeOGImage exports at 2× by default.
- Safe area
- The central region of a card that no platform crops. Keeping your headline and logo inside the safe area prevents important content from being cut off in feeds that trim the edges.
- Unfurl
- The act of a platform fetching a URL's tags and expanding the bare link into a rich preview card. A 'broken unfurl' is a link that fails to expand into an image card.
- Crawler / scraper
- The bot a platform sends to fetch your page's HTML and read its meta tags (e.g. facebookexternalhit). Crawlers usually don't run JavaScript, so your tags must be in the server-rendered HTML.
- Re-scrape
- Forcing a platform to fetch your page again and refresh its cached preview after you change tags. Use Facebook's Sharing Debugger or LinkedIn's Post Inspector.
- Caching
- Platforms store the first version of your tags they scrape and reuse it for a long time. This is why a fixed preview can still show the old image until you re-scrape.
- Absolute vs. relative URL
- An absolute URL includes the full domain (https://site.com/og/card.png); a relative one doesn't (/og/card.png). og:image must be absolute, because the crawler fetches it outside your page's context.
- Fallback image
- A default og:image used for pages that don't define their own, so links always have something to show instead of a blank card.