Last Updated: 2023-05-26 09:50:58 Friday
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universally unique identifier (UUID)is a
128-bitlabel used for information in computer systems. The term
globally unique identifier (GUID)is also used.
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.
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.
123e4567-e89b-12d3-a456-426614174000 xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx # version-1, variant-1
Form 8-4-4-4-12 for a total of 36 characters (32 hexadecimal characters and 4 hyphens). The four bits of digit M are the UUID version, and the 1 to 3 most significant bits of digit N code the UUID variant. In the example above, M is 1, and N is a (10xx2), meaning that this is a version-1, variant-1 UUID; that is, a time-based DCE/RFC 4122 UUID.
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