A UUID (Universally Unique Identifier) is a 128-bit label standardized by RFC 4122, represented as 36 characters in 8-4-4-4-12 hexadecimal format.

What is the difference between UUID v1 and v4?

UUID v1 is time-based, derived from the current timestamp and MAC address. UUID v4 is randomly generated, offering better privacy and no predictability.

Is a UUID the same as a GUID?

GUID is Microsoft's implementation of UUID, functionally identical. Both follow the same RFC 4122 standard and are interchangeable.

What is the probability of UUID collision?

The probability of a UUID v4 collision is astronomically low — roughly 1 in 5.3×10³⁶ for 1 billion UUIDs. It is negligible for practical purposes.

/ /UUID Generator & Validator

UUID Generator & Validator

Generate UUID v4 identifiers, validate UUID format, and detect versions. Supports single and bulk generation up to 100 UUIDs.

Inputs

Generate UUID v4

Bulk Generate

Validate UUID

Results

Generate a UUID or enter one to validate.

Related Tools

References

Frequently Asked Questions

What is a UUID?: A UUID (Universally Unique Identifier) is a 128-bit label standardized by RFC 4122, represented as 36 characters in 8-4-4-4-12 hexadecimal format.
What is the difference between UUID v1 and v4?: UUID v1 is time-based, derived from the current timestamp and MAC address. UUID v4 is randomly generated, offering better privacy and no predictability.
Is a UUID the same as a GUID?: GUID is Microsoft's implementation of UUID, functionally identical. Both follow the same RFC 4122 standard and are interchangeable.
What is the probability of UUID collision?: The probability of a UUID v4 collision is astronomically low — roughly 1 in 5.3×10³⁶ for 1 billion UUIDs. It is negligible for practical purposes.
How are UUIDs used in databases?: UUIDs serve as primary keys that are unique across tables, databases, and servers, eliminating key conflicts in distributed systems and replication.
What are the advantages of UUID over auto-increment IDs?: UUIDs are globally unique without coordination, resist enumeration attacks, and work across distributed systems. Auto-increment IDs are smaller and faster for indexing.
Can a UUID be serialized as JSON?: Yes, UUIDs are typically serialized as strings in JSON format. Some databases have native UUID types that serialize correctly.
What is UUID v5 and how does it differ from v3?: Both are name-based UUIDs. v3 uses MD5 hashing (128-bit), while v5 uses SHA-1 hashing (160-bit). Both generate the same UUID for the same namespace and name.
What is UUID v2?: UUID v2 is a DCE Security version derived from POSIX UID/GID. It is rarely used due to limited adoption and implementation complexity.
How do I validate a UUID?: A valid UUID matches the pattern: `/^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i`.
Can I use UUID as a session token?: UUIDs can be used as session identifiers, but cryptographically random tokens (e.g., 256-bit) are stronger for security-critical sessions.
What is the nil UUID?: The nil UUID is all zeros: `00000000-0000-0000-0000-000000000000`. It represents an absent or unknown UUID.
How are UUID bytes ordered?: UUID fields are stored in big-endian (network byte order) for fields 1-3, and little-endian for fields 4-5, varying by system implementation.
What is the maximum number of UUIDs that can be generated?: UUID v4 has 122 random bits, providing approximately 5.3×10³⁶ unique values — effectively inexhaustible for any practical application.