The following table lists some known namespaces. The second column corresponds to the prefix that is conventionally used to refer to the namespace.
| http://www.w3.org/1998/Math/MathML | math (?) | MathML |
| http://www.w3.org/1999/xhtml | | XHTML (« HTML when used with an XML serialisation»?) |
| https://www.w3.org/1999/xlink | | A namespace defined in the XML Linking Language (XLink) specification |
| http://www.w3.org/1999/XSL/Transform | xsl | XSLT |
| http://www.w3.org/2000/svg | | SVG |
| http://www.w3.org/2001/xml-events | | A namespace defined in the XML Events specification |
| http://www.w3.org/2001/XMLSchema | | XML Schema |
| https://www.w3.org/2001/XMLSchema-instance | | XML Schema instance namespace |
| http://www.w3.org/2002/xforms | | XForms (an XML application that represents the next generation of forms for the Web) |
| https://www.w3.org/2003/g/data-view | | GRDDL Data Views |
| http://purl.org/dc/elements/1.1/ | dc (?) | Dublin Core (A standard for metadata) |
| http://openoffice.org/2004/office | | |
| http://openoffice.org/2004/writer | | |
| http://openoffice.org/2004/calc | | |
| http://openoffice.org/2005/report | | |
| http://openoffice.org/2009/office | | |
| http://openoffice.org/2009/table | | |
| http://openoffice.org/2010/draw | | |
| urn:oasis:names:tc:opendocument:xmlns:XXX:1.0 | | OASIS: Open Document Format for Office Applications. XXX is one of animation, chart, config, database, dr3d, drawing, form, manifest, meta, data style, office, presentation, script, table, text, style, xsl-fo-compatible, svg-compatible, smil-compatible |