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UUID Generator

Generate RFC 4122 compliant UUID v4 unique identifiers instantly in your browser.

About the UUID Generator

A UUID (Universally Unique Identifier), also called a GUID (Globally Unique Identifier) in Microsoft contexts, is a 128-bit label used to uniquely identify information in computer systems. UUIDs are defined by RFC 4122 and are represented as 32 hexadecimal characters in the format xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx (e.g. 550e8400-e29b-41d4-a716-446655440000).

UUID versions

  • Version 1 — Generated from the current timestamp and the machine's MAC address. Guaranteed unique across time and space, but encodes when and where it was created, which can be a privacy concern.
  • Version 4 — Generated from random numbers. No information about the creator is encoded. This is the most widely used version for general-purpose unique identifiers.
  • Version 5 — Deterministic, generated by hashing a namespace and a name with SHA-1. The same input always produces the same UUID.

This tool generates Version 4 UUIDs using window.crypto.getRandomValues(), which provides cryptographically secure random numbers.

Common use cases

  • Database primary keys — UUIDs avoid sequential integer collisions when merging data from multiple sources or databases.
  • Distributed systems — Nodes can independently generate IDs without a central coordinator, since the probability of collision is astronomically small.
  • Session tokens and correlation IDs — Tracking requests across microservices or log systems.
  • File names — Avoiding name collisions for user-uploaded content.

Collision probability

The probability of generating two identical UUIDv4s is approximately 1 in 5.3 × 1036. In practice, UUIDs are considered globally unique for all purposes.

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Frequently asked questions

What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit label used to uniquely identify objects in computer systems. UUID v4 is randomly generated and has a collision probability so low it is effectively unique.
Are UUIDs truly unique?
UUID v4 uses 122 random bits, giving 2^122 possible values. The probability of a collision is astronomically low — you would need to generate billions per second for millions of years before a collision became likely.
Are UUIDs generated securely?
Yes. Generation uses window.crypto.getRandomValues() which is a cryptographically secure random number generator built into modern browsers.