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UUID

Tool to generate UUIDs (Universal Unique Identifier) from RFC 4122 and standardized ISO/IEC 9834-8:2008 compatible with version 3, 4 and 5

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Tag(s) : Hashing Function, Informatics

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UUID

UUID Generator

Random UUID (version 4)

Defined UUID (version 3 and 5)






UUID Version Reader


Answers to Questions (FAQ)

What is a UUID? (Definition)

A UUID (acronym for Universally Unique IDentifier) is an identifier that is intended to be unique and universal, defined by the ISO/IEC 9834-8:2008 standard. This is 128 bits of data usually displayed in hexadecimal in the format xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.

How to generate a UUID?

Version 4 is made up of random bits based on the timestamp of the system that generates them. The timestamp is usually shown in microseconds (one thousandth of a second) since a specific date (called EPOCH). The result is therefore pseudo-random and presents a very probable uniqueness (not guaranteed). Each time a UUID v4 is generated, the code generated is different.

Example: UUID v4 0cc12fda-deca-4f24-918b-f0884d2bb911

Version 3 is generated from an MD5 hash of a 2-part string: on one side a UUID named namespace , and on the other a character string containing the name to be encoded .

Version 5 is the same as version 3 but generated from a SHA-1 hash.

Each time a v3 or v5 UUID is generated, the generated code is always the same.

How to decode a UUID?

A version 4 UUID is completely random and contains nothing to decode.

A UUID version 3 or 5 can sometimes have been generated with a character string but it has been hashed with MD5 or SHA-1 cryptographic functions which are not intended to be decoded.

What are the versions of UUIDs?

UUIDs are generally categorized into different versions, ranging from version 1 to version 5.

Version 1: contains a timestamp and MAC address

Version 2: a variant of V1 for DCE (Distributed Computing Environment) which includes POSIX UIDs

Version 3: MD5 hash

Version 4: randomly generated

Version 5: SHA-1 hash

UUIDs also have a variant number (3 bits) assigned to them:

0xx: Reserved for NCS (Network Computing System) for backward compatibility

10x: Default variant, see RFC 4122

110: Reserved for Microsoft for backward compatibility

111: Reserved for future definition

How to recognize a UUID string?

The UUID code contains 128 bits presented in the form of 32 hexadecimal characters divided into 8-4-4-4-12 digits (base 16) and separated by a dash -

How to recognize the version of a UUID string?

Certain characters of the UUID string are marked, this is the case of the 13th byte (here denoted M) and the 17th byte (here denoted N) in a UUID xxxxxxxx-xxxx-Yxxx-Zxxx-xxxxxxxxxxxx

This is because Y and Z are hexadecimal digits specifying the version and variant of the UUID, respectively.

The value of Y corresponds directly to the version of the UUID

Example: If Y is 4, then it is a UUIDv4 (random)

The first 3 bits of Z (coded on 4 bits) correspond to the variant.

Source code

dCode retains ownership of the "UUID" source code. Except explicit open source licence (indicated Creative Commons / free), the "UUID" algorithm, the applet or snippet (converter, solver, encryption / decryption, encoding / decoding, ciphering / deciphering, breaker, translator), or the "UUID" functions (calculate, convert, solve, decrypt / encrypt, decipher / cipher, decode / encode, translate) written in any informatic language (Python, Java, PHP, C#, Javascript, Matlab, etc.) and all data download, script, or API access for "UUID" are not public, same for offline use on PC, mobile, tablet, iPhone or Android app!
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Cite as source (bibliography):
UUID on dCode.fr [online website], retrieved on 2024-03-29, https://www.dcode.fr/uuid-identifier

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