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CSS namespaces

files/en-us/web/css/guides/namespaces/index.md

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The CSS namespaces module defines the syntax for using {{glossary("namespace", "namespaces")}} in CSS.

CSS isn't just for styling HTML. A stylesheet may be used to style SVG, MathML, XML, or HTML, each of which has a different namespace or a document containing multiple namespaces.

The {{cssxref("@namespace")}} at-rule defined in this module enables distinguishing between same-named elements in different namespaces. Element tag names are not unique to a single language. For example, the <a> element isn't limited to HTML. You may want to style the <a>s within your SVGs differently from the links in your HTML. You also will likely want to ensure that {{domxref("Document.querySelectorAll", "querySelectorAll("a")")}} selects the right kind of element. Namespacing can help.

The @namespace rule is used for declaring a default namespace and for binding namespaces to namespace prefixes. The namespaces module also defines the syntax for using these prefixes to represent namespace-qualified names. That's it. What a name means or if the name is even valid depends on the context and host language.

Reference

At-rules and descriptors

  • {{cssxref("@namespace")}}

Guides

  • Namespaces crash course
    • : Deep dive into what a namespace is and how they are used in XML and XML-based markup languages.

Specifications

{{Specifications}}

See also