httpequiv

HTTP-equiv refers to an attribute of the HTML meta element that mirrors certain HTTP response headers and is interpreted by browsers to apply directives to a page. When used, a meta tag in the head section specifies a header name via the http-equiv attribute and a directive value via the content attribute. This provides a way to convey header-like information from the document itself, typically when server-side header configuration is unavailable or impractical.

Historically, http-equiv was used for a range of purposes, from specifying character encodings to controlling refresh behavior and browser compatibility modes. For example, a tag such as http-equiv="Content-Type" with a content value of "text/html; charset=UTF-8" was common before the charset attribute and explicit HTTP headers became standard. Modern HTML favors the simpler <meta charset="UTF-8"> and server-sent Content-Type. Other uses include http-equiv="refresh" with a content value that can trigger a timed refresh or redirect, and http-equiv="X-UA-Compatible" for Internet Explorer compatibility settings. Some servers also experimented with values like Cache-Control via http-equiv, but support for such directives is inconsistent.

Limitations include varied and sometimes limited browser support for http-equiv values, and the fact that many directives are better delivered as actual HTTP headers. Relying on http-equiv for critical behavior such as security or caching is discouraged, since server headers are generally more reliable and predictable. Additionally, not all search engines or accessibility tools treat http-equiv directives the same way as legitimate HTTP headers.

Best practice treats HTTP-equiv as a legacy mechanism. Use proper HTTP headers on the server for behavior related to caching, security, and redirects, and use modern, standards-compliant meta tags (such as charset) where appropriate. HTTP-equiv is most appropriate for legacy pages or situations where server configuration is not feasible.