Modern HTML allows for dozens of meta tags, but in practical SEO and web development you focus on six core tags and maybe eight to twelve additional ones depending on your goals. The big six are meta title (technically a title element, not a meta tag), meta description, charset (usually UTF-8), viewport (for mobile responsiveness), robots (to control indexing and crawling), and canonical (to prevent duplicate content issues). Those six appear on virtually every optimized page we build at Ottawa SEO. Beyond those, you often add Open Graph tags (og:title, og:description, og:image, og:url, og:type) for Facebook and LinkedIn sharing, plus Twitter Card tags (twitter:card, twitter:site, twitter:creator) for better tweet previews. If you run a multi-language site, hreflang goes in either meta tags or HTTP headers. For webmaster verification you might include Google Search Console, Bing Webmaster, or Pinterest meta tags temporarily. Less common but sometimes useful tags include meta refresh (usually avoided because it's clunky for UX), author, generator (WordPress loves to add this), theme-color for mobile browser chrome, and various Dublin Core tags for academic or archival content. Apple and Microsoft also defined proprietary tags like apple-mobile-web-app-capable or msapplication-TileColor, though those matter more for app-like experiences than SEO. The trap is over-tagging. Google ignores most meta keywords (deprecated since 2009), and stuffing irrelevant tags just bloats your HTML. At Ottawa SEO we typically deploy eight to ten meta tags per page: charset, viewport, title, description, canonical, robots, and two to four Open Graph or Twitter tags. More than that usually signals either a complex app or someone copy-pasting meta tag lists without understanding what each one does. Focus on the six core tags first, add social and technical tags as needed, and skip anything that doesn't serve a measurable SEO, UX, or sharing goal.