urn: URLs

A Uniform Resource Name (URN) is a URI that identifies a resource by name in a particular namespace. URNs provide globally-unique names for resources as opposed to providing information about their location (URL).

Syntax

urn:<NID>:<NSS>

• <NID>
  • : A NID (Namespace Identifier) is a case insensitive identifier for the namespace (e.g., ISBN and isbn are equivalent). NIDs are maintained by registries such as IANA, and their resolution depends on the specific namespace. For instance, the ISBN NID resolution is handled by International ISBN Agency systems.
• <NSS>
  • : The NSS (Namespace Specific String) is a string unique within a URN namespace. The combination of the NID (unique across the entire “urn” scheme) and the NSS ensures that the resulting URN is globally unique.

Examples

ISBN URN

This ISBN corresponds to the book Nineteen Eighty-Four by George Orwell:

urn:isbn:9780141036144

IETF URN

This URN corresponds to the IETF specification Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing:

urn:ietf:rfc:7230

Specifications

See also

• URIs
• What is a URL?
• IANA list of URI schemes