GlossaryTerms beginning with X
X-Robots-Tag
An indexing instruction sent in the HTTP header rather than the page. The only way to control indexing for files that have no HTML, such as PDFs.
XML Sitemap
The machine-readable sitemap format search engines read. Should list canonical, indexable URLs only; anything else wastes the signal it is meant to send.
Back to the full glossary, or read how we build them in From Zero to Hero.