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What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. UUIDs are standardized by the Open Software Foundation as part of the Distributed Computing Environment. The probability of duplicate UUIDs is astronomically low, making them ideal for distributed systems.

UUID Version 4 Format

Our generator creates UUID version 4, which is randomly generated. The format follows a specific pattern defined in RFC 4122:

  • xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
  • The digit 4 in the third segment indicates version 4
  • The y character is one of 8, 9, A, or B (indicating variant)
  • All other characters are random hexadecimal digits (0-9, a-f)

Common Use Cases

  • Database primary keys: Avoid ID collision across distributed databases
  • Session identifiers: Track user sessions without central coordination
  • API request IDs: Trace requests through microservices
  • File names: Generate unique filenames for uploaded files
  • Test data: Create realistic unique identifiers for development

Frequently Asked Questions

Are UUIDs truly unique?

While not mathematically guaranteed, the probability of collision is so low (roughly 1 in 2.71 quintillion) that for all practical purposes, they are unique.

Should I use UUID or GUID?

They are the same thing. Microsoft calls them GUIDs (Globally Unique Identifiers), while the rest of the world uses UUID. The format is identical.

Is this secure for tokens?

UUID v4 is random but not cryptographically secure. For security tokens, use a proper CSPRNG from your programming language standard library.