### Explanation Previews are the meta-layer summaries a platform exposes about a piece of content to crawlers, link unfurlers and embed renderers: Open Graph cards (og:title, og:image, og:description), Twitter Cards, oEmbed JSON, schema.org structured data, and the HTML `<meta>` tags that search engines pull into snippets. They exist so a page can be summarised consistently when shared in chat, embedded in a feed, or surfaced in a search result. Previews routinely leak data that the rendered page itself hides. A Google snippet may show a paragraph that's behind a paywall on the live page; an Open Graph image may be a higher-resolution or older version than the one in the post body; oEmbed JSON often contains an author display name and avatar even when the page renders only a username. Many platforms also let authors set a fully custom preview (Medium's social-share card, Substack's `og:image`, X's per-post preview, GitHub repo social images) — that custom preview can contain title, description or imagery that never appears on the page itself. Previews also outlive the content they describe. Google and Bing search snippets, link-unfurler caches (Slack, Discord, Telegram), and social-share endpoints typically hold onto the preview after the original page is deleted — sometimes for days, sometimes indefinitely. A removed post may still be partially recoverable from the cached snippet and OG image alone. Pull the preview directly via `curl`, view-source, an unfurl debugger (Facebook Sharing Debugger, Twitter Card Validator, Slack's link debugger), or by inspecting how the link expands in a messenger. ### Examples {{some links to articles, videos, etc}} ### Types technical ### See also - {{internal links to similar functionalities}} ### Typical weaknesses - {{internal links to typical weaknesses}}