XML namespace directory

The namespace every sitemap.xml and sitemap index must declare. Almost always the default namespace.

The namespace for Atom feeds, and for the <atom:link rel="self"> element that well-formed RSS feeds borrow.

The vocabulary a schema document is written in. Conventionally bound to xs: or xsd:.

Four attributes an instance document uses to point at its schema or declare a nil value.

The SOAP 1.1 envelope namespace. Distinct from SOAP 1.2 — the version is encoded in the URI.

The SOAP 1.2 envelope namespace, and the reason a 1.1 endpoint rejects a 1.2 message outright.

The service-description namespace for SOAP web services. Still the version almost every deployed WSDL uses.

The transformation-language namespace, unchanged across XSLT 1.0, 2.0 and 3.0.

Scalable Vector Graphics. Required for a standalone .svg file to render as an image.

XHTML markup — and, in sitemaps, the namespace that carries hreflang alternates.

Fifteen general-purpose metadata terms: creator, date, title, subject, rights and friends.

Supplies <content:encoded>, the element feeds use to carry full HTML article bodies.

The de facto podcast vocabulary: episode numbers, artwork, explicit flags and durations.

Declares the images belonging to each <url> entry in a sitemap.

Publication name, language and publication date for news articles in a sitemap.

Thumbnail, duration, player and content locations for video content in a sitemap.

The RDF graph syntax, and the namespace that identifies an RSS 1.0 document.

Describes a search endpoint, and adds paging metadata to search-result feeds.

Bound to the xml: prefix implicitly and permanently. Never declare it, never rebind it.

The localisation interchange format used to move translatable content between tools.

The root namespace for a UBL invoice, the basis of most European e-invoicing mandates.