Editing Universally unique identifier (section)

{{Short description|Label used for information in computer systems}}
{{infobox identifier
| name          = Universally Unique Identifier
| alt = Examples of Universally Unique Identifier (UUID) as used by EFI variables on Linux
| caption = Examples of Universally Unique Identifier (UUID) as used by EFI variables on Linux
| image         =Examples_of_universally_unique_identifier.png
| image_caption =
| image_alt     = 
| acronym       = UUID
| start_date    = <!-- {{Start date|YYYY|MM|DD|df=y}} -->
| organisation  = [[Open Software Foundation]] (OSF), [[International Organization for Standardization|ISO]]/[[International Electrotechnical Commission|IEC]], [[Internet Engineering Task Force]] (IETF)
| digits        = 32
| check_digit   = 
| example       = {{code|f81d4fae-7dec-11d0-a765-00a0c91e6bf6}}
| website       = {{IETF RFC|9562}} (obsoleted {{IETF RFC|4122}})
}}A '''Universally Unique Identifier''' ('''UUID''') is a [[128-bit]] [[nominal number|label]] used to uniquely identify objects in computer systems. The term '''Globally Unique Identifier''' ('''GUID''') is also used, mostly in [[Microsoft]] systems.<ref name="RFC 9562">{{cite IETF|title=Universally Unique IDentifiers (UUIDs)|rfc=9562|first1=K.|last1=Davis|first2=B.|last2=Peabody|first3=P.|last3=Leach|publisher=[[Internet Engineering Task Force]]|year=2024|access-date=2024-05-09}}</ref><ref name="RFC 4122">{{cite IETF|title=A Universally Unique IDentifier (UUID) URN Namespace|rfc=4122|first1=P.|last1=Leach|first2=M.|last2=Mealling|first3=R.|last3=Salz|publisher=[[Internet Engineering Task Force]]|year=2005|access-date=2017-01-17}}</ref>

When generated according to the standard methods, UUIDs are, for practical purposes, unique. Their uniqueness does not depend on a central registration authority or coordination between the parties generating them, unlike most other numbering schemes. While the [[probability]] that a UUID will be duplicated is not zero, it is generally considered close enough to zero to be negligible.<ref>{{cite web |title=Universally Unique Identifiers (UUID) |url=http://www.h2database.com/html/advanced.html#uuid |access-date=21 March 2021 |website=[[H2 (DBMS)|H2]] |language=en-US}}</ref><ref>''ITU-T Recommendation [https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-X.667-201210-I!!PDF-E&type=items X.667]: Generation and registration of Universally Unique Identifiers (UUIDs) and their use as ASN.1 Object Identifier components''. Standard. October 2012.</ref>

Thus, anyone can create a UUID and use it to identify something with near certainty that the identifier does not duplicate one that has already been, or will be, created to identify something else. Information labeled with UUIDs by independent parties can therefore be later combined into a single database or transmitted on the same channel, with a negligible probability of duplication.

Adoption of UUIDs is widespread, with many computing platforms providing support for generating them and for parsing their textual representation.{{TOC limit|3}}