Invalid UUID Variant – Check RFC 4122 Variant Bits

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Show how a valid-looking UUID can fail because its fourth-group variant nibble is outside the accepted RFC range.

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Invalid RFC 4122 UUID

UUID variant bits

Why does this UUID fail the RFC 4122 variant check?

After canonical format and version checks, VetaTool reads the first hexadecimal character of the fourth group. The validator accepts the RFC 4122 variant range represented by hexadecimal 8 through B; the example starts with 7 and is rejected. This tool is free to use. No account or payment is required.

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What you can do here

  • Canonical 8-4-4-4-12 UUID validation
  • UUID version inspection
  • RFC 4122 variant checking
  • Nil UUID recognition
  • Uppercase hexadecimal support
  • Browser-local validation

Steps

  1. Confirm the UUID uses canonical text format.
  2. Check the first hexadecimal digit of the fourth group.
  3. For this validator, confirm that digit is 8, 9, A, or B.

The RFC variant is encoded separately from the version

A UUID may carry a version 4 nibble while still failing the variant test. VetaTool reports both unsupported version and unsupported variant cases with the same invalid RFC 4122 UUID label after format matching succeeds.

Invalid variant example

The fourth group starts with 7, outside the accepted RFC 4122 variant range.

UUID input

550e8400-e29b-41d4-7716-446655440000

Validation result

Invalid RFC 4122 UUID

Common questions

Frequently asked questions

Which variant nibbles does VetaTool accept?

The current validator accepts hexadecimal 8 through B for the first digit of the fourth group.

Is the variant the same thing as the UUID version?

No. The version is read from the third group, while the variant is read from the fourth group.

Recommended next steps

Invalid UUID VersionInspect a canonical UUID shape whose version nibble falls outside versions 1 through 8.UUID Version DetectionRead the version nibble from a canonical UUID and identify values such as UUID v1.UUID Generator & Validator OnlineGenerate UUID v4 batches or validate canonical UUID format, version, and variant locally.

Debugging a specific UUID issue? Browse UUID troubleshooting.