URIs, URLs, and URNs


URIs, URLs, and URNs In September 2001, the W3C issued a note clarifying the terms URI (Uniform Resource Identifier), URL (Uniform Resource Locator), and URN (Uniform Resource Name).

The key difference between these three categories of identifiers are:

  • URI and IRI are the terms for any type of identifier used to identify a resource on the Web.
  • URL is the term for any type of URI that can be resolved or de-referenced to locate a representation of a resource on the Web (e.g., Web page, file, image, etc.)
  • URN is the term for a specific type of URI intended to persistently identify a resource
    (i.e., an identifier that will never change no matter how often the resource moves, changes names, changes owners, etc. URNs are intended to last forever.)

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