UUID Validator & Checker
Quickly check if your string is a valid UUID. This validator ensures your identifier follows the official RFC 4122 format, checking length, hex characters, hyphens, and version/variant bits. Get immediate feedback on any errors.
UUID Validator
Validate UUID format and extract version and variant information.
UUID Format
A valid UUID follows this pattern: 8-4-4-4-12 hexadecimal digits
xxxxxxxx-xxxx-Vxxx-Nxxx-xxxxxxxxxxxxV = Version (1-5)
N = Variant (8, 9, A, or B for RFC 4122)
How the UUID Validator Works
This validator checks if your input matches the RFC 4122 UUID format using a regular expression pattern. It extracts the version and variant bits from their fixed positions within the UUID structure.
The validation happens entirely in your browser. The tool parses the 128-bit value, identifies which bits represent the version (bits 48-51) and variant (bits 64-67), then displays human-readable information about what those bits mean.
UUID structure breakdown:
xxxxxxxx-xxxx-Vxxx-Nxxx-xxxxxxxxxxxxReal Use Cases
Debugging API responses
A developer receives a UUID from an API and needs to quickly verify it's properly formatted before using it in subsequent requests.
Data migration validation
After migrating a database, an engineer checks that all UUID fields maintained their format and identifies any corrupted entries.
Log file analysis
Someone parsing logs needs to extract and validate UUIDs to trace requests across distributed services.
Form input validation
A frontend developer is building a form where users paste UUIDs and needs to show real-time validation feedback.
Learning UUID structure
A student studying distributed systems wants to understand how version and variant bits work in practice.
Legacy system integration
An engineer encounters GUIDs from a Windows system and needs to verify they're compatible with RFC 4122 UUIDs.
What to Know Before Using
Format requirements: The validator expects the standard 8-4-4-4-12 hyphenated format. UUIDs without hyphens or with braces will fail validation even if the underlying value is valid.
Case insensitive: Both uppercase and lowercase hexadecimal characters are accepted. 550E8400 and 550e8400 are equally valid.
Version validation: Only versions 1-5 are considered valid. If you encounter version 0 or 6+, the UUID is either malformed or uses a non-standard extension.
Variant matters: RFC 4122 UUIDs (the standard) have variant bits 8, 9, A, or B. Other values indicate Microsoft GUIDs or reserved formats that may not be compatible with all UUID libraries.
FAQ
What makes a UUID valid?
A valid UUID has exactly 32 hexadecimal digits displayed in 5 groups (8-4-4-4-12) separated by hyphens. The 13th character must be 1-5 (version), and the 17th character should be 8, 9, A, or B (RFC 4122 variant).
What are the different UUID versions?
Version 1 uses timestamp and MAC address. Version 2 is DCE Security (rarely used). Version 3 is name-based with MD5. Version 4 is random. Version 5 is name-based with SHA-1. Each version serves different use cases.
Why does my UUID show as invalid?
Common reasons: missing hyphens, wrong character count, invalid hex characters (G-Z), version digit outside 1-5, or variant digit not in 8, 9, A, B range. Check the exact format against the pattern shown above.
What's the difference between RFC 4122 and Microsoft variants?
RFC 4122 UUIDs have variant bits 8, 9, A, or B. Microsoft GUIDs (older format) use variant bits C, D, E, or F. Modern systems typically use RFC 4122, but Windows systems may still generate the Microsoft variant.
Can I validate UUIDs without hyphens?
This validator requires hyphens for consistency. If you have a hyphen-free UUID, add them at positions 8, 12, 16, and 20. Or use the UUID Case Formatter tool to convert between formats.
What does "normalized" mean in the output?
Normalized means the UUID converted to lowercase with standard hyphenation. This is the canonical RFC 4122 text representation, useful for consistent comparison and storage.
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