What Data Type Is a UUID?


Heather Bennett

What Data Type Is a UUID?

A UUID, or Universally Unique Identifier, is a data type that is used to uniquely identify information in computer systems. It is a string of characters that is generated using specific algorithms and typically represented by 32 hexadecimal digits separated by hyphens.

UUID Structure

A UUID consists of five groups of characters separated by hyphens. The first group has 8 characters, the second and third groups have 4 characters each, the fourth group has 12 characters, and the fifth group has 4 characters. Each character can be any hexadecimal digit (0-9 or A-F).

UUID Versions

There are different versions of UUIDs, each with its own algorithm for generating unique identifiers:

Version 1

This version uses the MAC address of the network interface card (NIC) and a timestamp as part of its generation process. It guarantees uniqueness if the MAC address is unique.

Version 2

This version includes additional information such as the user’s POSIX UID/GID (User ID/Group ID). However, it is not widely used and considered less reliable for generating unique identifiers.

Version 3

This version uses MD5 hashing to generate a UUID based on a namespace identifier and an input name or value. It ensures uniqueness within a given namespace but does not guarantee global uniqueness.

Version 4

This version generates UUIDs purely based on random numbers. It offers a high level of randomness and uniqueness but does not guarantee it.

Version 5

This version is similar to Version 3 but uses SHA-1 hashing instead of MD5. It also generates a UUID based on a namespace and an input name or value.

Usage of UUIDs

UUIDs are commonly used in various scenarios:

  • Database primary keys: UUIDs can be used as primary keys in databases instead of auto-incrementing integers. This allows for distributed systems and avoids conflicts when merging data from different sources.
  • Web applications: UUIDs can be used as unique identifiers for resources such as user accounts, sessions, or URLs.
  • Message queues: UUIDs can be used as message IDs in message queuing systems to ensure uniqueness and track messages across different components.


A UUID is a data type that provides a unique identifier for information within computer systems. With different versions available, UUIDs can be generated based on various algorithms and serve a wide range of use cases across different industries.

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