A meta-tag protocol introduced by Facebook in 2010 that lets a page declare how it should appear when shared on social platforms — title, description, image, type, canonical URL. Tags use the
og: namespace, e.g. <meta property="og:title" content="...">. Adopted by virtually every major social platform (LinkedIn, Slack, Discord, iMessage previews) and many messaging apps. Often used as fallbacks by search engines when no other source is available. Increasingly important as social and chat-app traffic competes with organic search.