A URN (Uniform Resource Name) is a unique, permanent identifier for a resource – independent of where it currently sits or how it’s retrieved. While a URL specifies a resource’s location (e.g. https://example.com/buch.pdf), a URN describes only its identity (e.g. urn:isbn:978-3-86680-192-9). URNs are part of the overarching family of Uniform Resource Identifiers (URIs), to which URLs also belong.
Structure of a URN
A URN follows a fixed scheme, defined in RFC 8141:
urn:<NID>:<NSS>
urn: the fixed prefix signalling the schemeNID(namespace identifier) – a registered namespace, e.g.isbn,uuid,ietfNSS(namespace specific string) – the actual identifier within the namespace
Examples:
urn:isbn:978-3-86680-192-9
urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6
urn:doi:10.1109/5.771073
urn:nbn:de:bvb:355-ubr14358-9
urn:ietf:rfc:3987
URL vs. URI vs. URN
The three terms are frequently confused in everyday use:
| Term | What it describes | Example |
|---|---|---|
| URI | The umbrella term for any unique identifier | https://example.com/page or urn:isbn:… |
| URL | A URI that also describes the access path | https://example.com/page |
| URN | A URI describing only the identity, without an access path | urn:isbn:978-3-86680-192-9 |
Mnemonic: every URL and every URN is a URI, but not the other way round.
What are URNs used for?
URNs make sense where a resource needs a permanent identity mark outlasting its storage location, i.e. location changes, server migrations or publisher changes:
urn:isbn:…: books with an International Standard Book Numberurn:issn:…: journals with an International Standard Serial Numberurn:doi:…: scientific publications with a Digital Object Identifierurn:uuid:…: universally unique identifiers, ubiquitous in softwareurn:epc:…: electronic product codes for RFID/EAN trackingurn:nbn:…: national library identifiers (in Germany, e.g. the DNB)
URNs in practice – where do they pay off?
In web development and marketing websites, the URN plays hardly any role today – there the URL dominates. URNs are, in contrast, widespread in:
- Science & libraries: DOIs and national identifiers for citable references
- XML namespaces: frequently declared as URNs (
xmlns="urn:..."), even though URLs are allowed - Software development: UUIDs in URN form (
urn:uuid:...) in databases, logs and APIs - Industry standards: EPC for supply chains, SOAP schemas, identity federation
Differences from DOI and permalink
A DOI (Digital Object Identifier) is one concrete URN form, combined with a resolver service turning DOI into URL, i.e. identity + lookup. A permalink, in contrast, is a URL that’s meant to be long-term stable but technically remains a URL.
Frequently asked questions about URNs
Can you type a URN into a browser?
In theory yes, in practice no – browsers can’t resolve the urn: scheme on their own. An external resolver (DOI resolver, ISBN search) is needed to map the URN to a concrete URL.
When should I use a URN instead of a URL? When the identifier should be persistent and the storage location may change. That’s rarely relevant for web content, but the standard for archiving, scientific citations and industry identifiers.
Is urn:uuid:… the same as a UUID?
A UUID is the value (e.g. f81d4fae-7dec-11d0-a765-00a0c91e6bf6); urn:uuid:… is the variant formally packaged into the URN scheme. Substantively the same.
Conclusion
URNs solve a concrete problem: stable, location-independent identity for resources that remain findable even when the URL changes. In everyday web development you rarely encounter them – in scientific, library or identity management contexts, regularly. Anyone building a website or application with archival ambitions should at least know the concept exists. We’re happy to advise you on the fitting strategy – get in touch for a no-obligation consultation.