docs/rfc4122.rst
.. _rfc4122:
.. toctree:: :titlesonly: :hidden:
rfc4122/version1
rfc4122/version2
rfc4122/version3
rfc4122/version4
rfc4122/version5
rfc4122/version6
rfc4122/version7
rfc4122/version8
RFC 9562_ (formerly RFC 4122_) defines eight versions of UUIDs. Each version has different generation algorithms and
properties. Which one you choose depends on your use-case. You can find out more about their applications on the
specific page for that version.
Version 1: Gregorian Time
This version of UUID combines a timestamp, node value (in the form of a MAC address from the local computer's
network interface), and a clock sequence to ensure uniqueness. For more details, see :doc:rfc4122/version1.
Version 2: DCE Security
This version of UUID is the same as Version 1, except the clock_seq_low field is replaced with a local domain
and the time_low field is replaced with a local identifier. For more details, see :doc:rfc4122/version2.
Version 3: Name-based (MD5)
This version of UUID hashes together a namespace and a name to create a deterministic UUID. The hashing algorithm
used is MD5. For more details, see :doc:rfc4122/version3.
Version 4: Random
This version creates a UUID using truly-random or pseudo-random numbers. For more details, see :doc:rfc4122/version4.
Version 5: Named-based (SHA-1)
This version of UUID hashes together a namespace and a name to create a deterministic UUID. The hashing algorithm
used is SHA-1. For more details, see :doc:rfc4122/version5.
Version 6: Reordered Gregorian Time
This version of UUID combines the features of a :ref:version 1 UUID <rfc4122.version1> with a monotonically
increasing UUID. For more details, see :ref:rfc4122.version6.
Version 7: Unix Epoch Time
This version of UUID combines a timestamp--based on milliseconds elapsed since the Unix Epoch--and random bytes to
create a monotonically increasing, sortable UUID without the privacy and entropy concerns associated with version 1
and version 6 UUIDs. For more details, see :ref:rfc4122.version7.
Version 8: Implementation-Specific, Custom Format
This version of UUID allows applications to generate custom identifiers in an RFC-compatible format. For more
details, see :doc:rfc4122/version8.
.. _RFC 4122: https://www.rfc-editor.org/rfc/rfc4122 .. _RFC 9562: https://www.rfc-editor.org/rfc/rfc9562