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UUID / GUID v4 Generator Online

Generate universally unique identifiers (UUID Version 4) in bulk using browser-native cryptographically strong pseudo-random number generators (CSPRNG).

Case Formatting:
Hyphens:
Generated 5 UUIDs
Entropy Source: Web Crypto CSPRNG
RFC 4122 Compliant Version 4

What is a Version-4 UUID (GUID)?

A Universally Unique Identifier (UUID)—also known across the Microsoft ecosystem as a Globally Unique Identifier (GUID)—is a 128-bit label standardized under RFC 4122. In its canonical text representation, a UUID is displayed as 32 hexadecimal digits grouped into five hyphen-separated blocks: 8-4-4-4-12 (for example, c2d4e79b-4395-4bf4-9983-5a0224d4e389).

While earlier specifications derived identifiers from network MAC addresses (v1) or namespaces (v3/v5), UUID Version 4 is generated entirely from pseudo-random numbers. Out of the 128 total bits, 122 bits represent pure cryptographic randomness, providing 2^122 (approximately 5.3 × 10^36) possible unique values.

What is the Probability of a UUID v4 Collision?

The likelihood of generating two identical UUIDs at random is astronomically small. To put this in perspective:

  • To have a 50% probability of generating a single collision, you would need to produce 1 billion UUIDs per second continuously for roughly 85 years (approximately 2.71 quintillion UUIDs).
  • In a distributed database holding 1 trillion items, the probability of an identifier collision is less than one in a billion.

Frequently Asked Questions

Yes. GUID is Microsoft's implementation of the open standard UUID (RFC 4122). For all practical development purposes, they are identical in structure and bit length.
ToolCardio generates identifiers directly through your browser's native crypto.randomUUID() or crypto.getRandomValues() API, which harnesses operating-system-level entropy (hardware noise and CPU interrupts).