Websites embed structured metadata in HTML for search engines and social media. Open Graph and Twitter Cards control how links appear when shared. Understanding this metadata helps build SEO tools and content aggregators.
Standard Meta Tags
Meta tags in the <head> section provide page information. <title> sets the page title. <meta name="description"> provides the summary shown in search results. <meta name="keywords"> is largely ignored by modern search engines. <meta name="robots"> controls indexing. These tags are fundamental for SEO and appear in all well-structured websites.
Open Graph Protocol
Open Graph (og:) tags control how URLs appear when shared on Facebook, LinkedIn, Slack, etc. og:title, og:description, and og:image are essential. og:type specifies content type (article, website, video). og:url should be the canonical URL. If og: tags are missing, platforms fall back to standard meta tags. Most websites include og: tags for better social sharing.
Twitter Cards
Twitter Cards (twitter:) tags customize appearance on Twitter. twitter:card specifies card type (summary, summary_large_image, player). twitter:title and twitter:description override og: tags for Twitter. If twitter: tags are missing, Twitter uses og: tags. Most sites use og: tags only since Twitter supports them.