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UUID Format & Version Validator
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This UUID validator checks whether a string is a correctly formatted universally unique identifier and identifies its version - v1, v3, v4, v5, or nil - along with its variant bits. It's a quick reference for developers debugging identifier fields in a database, API responses, or logs where the exact UUID version matters, such as distinguishing a timestamp-based v1 UUID from a random v4 one. Rather than manually inspecting the version nibble in the UUID string, this check uuid tool parses the structure and tells you immediately whether it's valid and which algorithm generated it. It's especially useful when working with systems that mix UUID versions, or when validating that user-submitted identifiers conform to the expected format before processing them further. Validation happens instantly in your browser with nothing ever transmitted. Paste a UUID below to validate its format and see its version and variant.
Features
- Validates standard 8-4-4-4-12 UUID format
- Identifies UUID version (v1, v3, v4, v5) from the version nibble
- Detects and labels the variant bits (RFC 4122, Microsoft, etc.)
- Flags malformed or incorrectly hyphenated UUIDs
- Recognizes the special nil UUID (all zeros)
- Instant validation as you type or paste
- Case-insensitive input handling
Why use this uuid format & version validator?
- Instant validation with no manual bit inspection
- Fully private - UUIDs are never sent anywhere
- Accurate version and variant detection per RFC 4122
- Useful for both quick checks and deeper debugging
- Free with unlimited validations
Frequently asked questions
What's the difference between UUID v1 and v4?
UUID v1 is generated from a timestamp and node identifier (often MAC address), while UUID v4 is generated using random or pseudo-random bytes with no embedded meaning.
How can I tell what version a UUID is just by looking at it?
The version is encoded in the first character of the third group; for example, a UUID like xxxxxxxx-xxxx-4xxx-xxxx-xxxxxxxxxxxx with a '4' there is version 4.
What is the nil UUID?
The nil UUID is a special reserved value consisting of all zeros (00000000-0000-0000-0000-000000000000), often used to represent an absent or unset identifier.
Are UUID v3 and v5 different from v1 and v4?
Yes, v3 and v5 are generated deterministically by hashing a namespace and name using MD5 (v3) or SHA-1 (v5), producing the same UUID every time for the same input.
Is GUID the same thing as UUID?
GUID is Microsoft's term for essentially the same concept as UUID; they follow the same 128-bit structure with minor historical formatting differences.
Does this tool check for duplicate UUIDs?
No, it validates format and version for a single UUID; duplicate detection would require comparing against a known dataset.
What does the 'variant' field indicate in a UUID?
The variant bits indicate which layout rules the UUID follows; most modern UUIDs use the RFC 4122 variant, distinguishing them from older or vendor-specific formats.