HTML meta tags are elements placed in the head section of an HTML document that provide metadata about the page to browsers, search engines, and social media platforms. The term "meta" comes from the HTML meta element, but in practice "meta tags" encompasses the title element, meta elements, and link elements that collectively define a page's metadata profile. These tags do not appear visually on the page but profoundly influence how the page is indexed, displayed in search results, and presented when shared on social platforms.

SEO metadata begins with the title tag, the single most important on-page SEO element, which appears in browser tabs, search engine results, and social media shares. Search engines typically display the first 50-60 characters of a title, making concise, keyword-rich titles essential. The meta description provides a summary that search engines may display as the snippet beneath the title in search results. While Google has confirmed that meta descriptions are not a direct ranking factor, a compelling description significantly affects click-through rates, making it an indirect but important SEO element. The meta robots tag controls search engine behavior with directives like index/noindex (whether to include the page in search results), follow/nofollow (whether to follow links on the page), and noarchive (whether to cache the page).

Structured data and social sharing metadata extend beyond basic SEO. Open Graph tags (og:title, og:description, og:image, og:url), developed by Facebook and adopted by LinkedIn, Pinterest, and other platforms, control how links appear when shared on social media. Twitter Cards (twitter:card, twitter:title, twitter:description, twitter:image) provide Twitter-specific sharing metadata that can display content as summary cards, large image cards, or app install cards. The canonical URL (link rel="canonical") signals to search engines which URL is the definitive version of a page, consolidating ranking signals when the same content is accessible through multiple URLs.

Search engine indexing relies on crawling and parsing these meta tags to understand page content and context. The title and description form the search result snippet, while structured data (JSON-LD, Microdata, or RDFa) provides machine-readable context about the page content, potentially enabling rich results like recipe cards, event listings, product ratings, and FAQ accordions. The hreflang tag signals language and regional targeting for multilingual sites. The viewport meta tag, while not SEO-specific, is essential for mobile usability, which Google uses as a ranking signal. Together, these metadata elements form a comprehensive communication layer between web pages and the platforms that index, display, and share them.