X-Robots-Tag is an HTTP response header that allows robots directives — such as noindex, nofollow, noarchive, nosnippet, and max-snippet — to be applied to any type of resource, not just HTML pages. Because the directives are delivered at the header level rather than within the document body, X-Robots-Tag is the only practical mechanism for applying robots instructions to PDFs, images, videos, and other non-HTML files. It also allows directives to be applied server-side to entire URL patterns without modifying individual pages, which can be useful at scale. Multiple directives can be combined in a single header or in multiple X-Robots-Tag headers. The header can target specific crawlers by including the bot’s name before the directive (for example, Googlebot: noindex), leaving other bots unaffected. Equivalence with the meta robots tag makes the two methods interchangeable for HTML pages, and both are honoured by Google.