Uniform Resource Name (RFC 8141), a URI of the form urn:NID:NSS where NID is a registered Namespace Identifier and NSS is the namespace-specific string, intended to denote a resource persistently and independently of any particular resolution mechanism.

ByCASRAI Editorial Board

· Last updated 10 Jul 2026

Examples

Worked examples

Is an instance
urn:isbn:0-486-27557-4 (a book).
Is an instance
urn:nbn:de:bsz:14-qucosa-123456 (a German national bibliography number).

Counter-examples

Looks similar, but isn't

Not an instance
https://example.org/paper.pdf is a URL, not a URN.
Not an instance
A DOI in its HTTPS form (https://doi.org/...) is a URL even though it names persistently.

Editorial commentary

URNs are one of the three families of URIs alongside URLs and URCs in early IETF terminology. A URN does not by itself imply resolution: it names a resource but does not (necessarily) tell you where to get it. Namespaces are registered with IANA; common examples include urn:isbn:, urn:issn:, urn:uuid:, urn:nbn: (National Bibliography Number), urn:doi: (deprecated but historically used), and urn:lex:. National libraries, especially in Germany, Finland, and the Netherlands, use urn:nbn: prefixes at large scale.

References

Saint-Andre P., Klensin J., RFC 8141, 'Uniform Resource Names (URNs)', IETF, 2017.

Also known as

Uniform Resource Name

Machine-readable encodings

Use in your systems

JATS XML <role> element

xml

<role vocab="credit"
      vocab-identifier="https://casrai.org/dictionary/"
      vocab-term="URN"
      vocab-term-identifier="https://casrai.org/dictionary/term/urn" />

Schema.org DefinedTerm (JSON-LD)

json

{
  "@context": "https://schema.org",
  "@type": "DefinedTerm",
  "@id": "https://casrai.org/dictionary/term/urn",
  "name": "URN",
  "identifier": "https://casrai.org/dictionary/term/urn",
  "description": "Uniform Resource Name (RFC 8141), a URI of the form urn:NID:NSS where NID is a registered Namespace Identifier and NSS is the namespace-specific string, intended to denote a resource persistently and independently of any particular resolution mechanism.",
  "inDefinedTermSet": "https://casrai.org/dictionary/domain/persistent-identifiers#set",
  "url": "https://casrai.org/dictionary/term/urn",
  "sameAs": [
    "Uniform Resource Name"
  ],
  "license": "https://creativecommons.org/licenses/by/4.0/",
  "publisher": {
    "@id": "https://casrai.org/#organization"
  },
  "dateModified": "2026-07-10T02:06:20",
  "inLanguage": "en"
}

Referenced across the research world

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