Examples
Worked examples
- Is an instance
550e8400-e29b-41d4-a716-446655440000 (a v4, random UUID).
- Is an instance
urn:uuid:f47ac10b-58cc-4372-a567-0e02b2c3d479 (a UUID expressed as a URN).
Counter-examples
Looks similar, but isn't
- Not an instance
An ORCID iD has only 64 bits of randomness in a different format and is not a UUID.
- Not an instance
A DOI's suffix is not itself a UUID, though a registrant may choose to use one as the suffix.
Editorial commentary
A UUID (Universally Unique Identifier) is a 128-bit value, standardised by IETF RFC 4122 (2005) and its 2024 successor RFC 9562, rendered as 32 hexadecimal digits in 8-4-4-4-12 grouping (e.g. 550e8400-e29b-41d4-a716-446655440000). It is generated such that the probability of collision between independently generated UUIDs is negligible, without requiring any central issuing authority.
Versions in brief
RFC 4122 defined version 1 (timestamp plus network-card address), versions 3 and 5 (deterministic, hashed from a namespace and a name), and version 4 (random). RFC 9562 (2024) is a direct successor, not a replacement scheme, and added versions 6-8, including time-ordered variants designed to sort well as database keys.
Scope note
UUIDs are a general-purpose computing identifier used across essentially all software, not a research-specific standard — most of what there is to say about UUID generation, collision probability, or database-key design is programming reference material, not research-administration content, and is covered far more thoroughly by RFC 4122/9562 themselves and general software documentation than a research-standards page usefully can. This entry keeps to the research-data-management angle: where and why UUIDs show up in research infrastructure.
Where UUIDs show up in research infrastructure
Many repository and CRIS platforms use a UUID as the internal database primary key for a record the moment it is created, before, or instead of, registering an external persistent identifier for it. Some registrants also choose a UUID as the opaque DOI suffix string itself, rather than an incrementing counter or a semantic pattern. Either way, a bare UUID carries none of the resolution or governance guarantees a registered persistent identifier has — see GUID for the closely related Microsoft-originated term and how the two relate and differ.
Frequently asked questions
Is a UUID the same thing as a GUID?
Structurally, a Microsoft GUID is the Variant-2 UUID format under a different name — see the GUID entry for the full distinction, including GUID’s looser informal usage outside Microsoft platforms.
Can a UUID be used as a citable identifier for a dataset?
Not on its own — a bare UUID has no external resolution service or governing registration agency behind it. A registered DOI, which may itself use a UUID as its opaque suffix, is the citable identifier; the UUID alone is not.
References
- Leach, P., Mealling, M., Salz, R., RFC 4122: A Universally Unique IDentifier (UUID) URN Namespace, IETF, 2005.
- Davis, K., Peabody, B., Leach, P., RFC 9562: Universally Unique IDentifiers (UUIDs), IETF, 2024.
Also known as
Universally Unique Identifier
Machine-readable encodings
Use in your systems
<role vocab="credit"
vocab-identifier="https://casrai.org/dictionary/"
vocab-term="UUID"
vocab-term-identifier="https://casrai.org/dictionary/term/uuid" />{
"@context": "https://schema.org",
"@type": "DefinedTerm",
"@id": "https://casrai.org/dictionary/term/uuid",
"name": "UUID",
"identifier": "https://casrai.org/dictionary/term/uuid",
"description": "Universally Unique Identifier (RFC 4122 / ISO/IEC 9834-8), a 128-bit value rendered as 32 hexadecimal digits in 8-4-4-4-12 grouping, generated such that the probability of collision across independent generators is negligible.",
"inDefinedTermSet": "https://casrai.org/dictionary/domain/persistent-identifiers#set",
"url": "https://casrai.org/dictionary/term/uuid",
"sameAs": [
"Universally Unique Identifier"
],
"license": "https://creativecommons.org/licenses/by/4.0/",
"publisher": {
"@id": "https://casrai.org/#organization"
},
"author": {
"@id": "https://casrai.org/#editorial-team"
},
"datePublished": "2026-05-21T02:10:16",
"dateModified": "2026-08-22T15:52:39",
"inLanguage": "en-GB",
"isAccessibleForFree": true
}
