This is a work in progress! For the latest updates from the HTML WG, possibly including important bug fixes, please look at the editor's draft instead. There may also be a more up-to-date Working Draft with changes based on resolution of Last Call issues.
The HTML namespace is:
The MathML namespace is:
The SVG namespace is:
The XLink namespace is:
The XML namespace is:
The XMLNS namespace is:
Data mining tools and other user agents that perform operations on content without running scripts, evaluating CSS or XPath expressions, or otherwise exposing the resulting DOM to arbitrary content, may "support namespaces" by just asserting that their DOM node analogues are in certain namespaces, without actually exposing the above strings.
In the HTML syntax, namespace prefixes and namespace declarations do not have the same effect as in XML. For instance, the colon has no special meaning in HTML element names.