An HTTP response header is metadata sent by a server back to a browser or crawler alongside a webpage’s content, providing information like the status code, content type, caching instructions, and sometimes SEO-relevant directives like X-Robots-Tag.
Response headers can carry important SEO directives even when a corresponding HTML meta tag isn’t present, such as using an X-Robots-Tag header to apply a noindex directive to non-HTML files like PDFs, which can’t contain a meta tag.
Reviewing HTTP response headers directly, using browser developer tools or specialized SEO crawlers, helps catch directives that might not be visible when simply viewing a page’s source HTML.
We review HTTP response headers as part of our Technical SEO audits.