A Uniform Resource Name (URN) is a Uniform Resource Identifier (URI) that uses the urn scheme, and does not imply availability of the identified resource. Both URNs (names) and URLs (locators) are URIs, and a particular URI may be a name and a locator at the same time.

RFC 2141 says:

Uniform Resource Names (URNs) are intended to serve as persistent, location-independent resource identifiers and are designed to make it easy to map other namespaces (that share the properties of URNs) into URN-space. Therefore, the URN syntax provides a means to encode character data in a form that can be sent in existing protocols, transcribed on most keyboards, etc.

Comparison with URLs

Suppose you own a copy of the book named The Last Unicorn.

If you tell someone, "My copy of the book is on the lightstand in my bedroom," that's like a URL — you're telling someone where something is.

But, if you tell someone, "I read a neat book; it's called The Last Unicorn," then that's like a URN — you're telling someone the name of something.

If you tell a person where a particular copy is (give them the URL), they can get it for you, or tell someone else where it is.

If you tell a person the book's (resource's) name (give them the URN), they can reason about it—they can tell if they've seen it before, maybe they can talk about what's inside the story, and they may be able to get it for you if they can map the name (URN) to a location (URL). Most importantly, you've established a context—you can discuss the book with no need to retrieve it or know where it is located.

You could tell somebody: "You can find urn:ietf:rfc:3187 (URN) over at http://www.faqs.org/rfcs/rfc3187.html (URL)."

Examples

• "urn:isbn:0451450523" - the URN for "The Last Unicorn", identified by its book number.
• "urn:ietf:rfc:3187" - the URN for the IETF's RFC 3187.
• "urn:oid:2.16.840" - the URN corresponding to the OID for the United States.
• "urn:sha1:YNCKHTQCWBTRNJIV4WNAE52SJUQCZO5C" - the URN representing an exact MP3 file of the I have a dream speech by Martin Luther King.
• "urn:uuid:6e8bc430-9c3a-11d9-9669-0800200c9a66" - a URN using a version 1 UUID.

See also

• DOI (digital object identifier)
• PURL

External links

• Uniform Resource Names Charter - The IETF's Uniform Resource Names working group
• IANA URN namespace assignments

URI scheme | Internet standards | Identifiers

Uniform Resource Name | Uniform Resource Name | URN | URN