What Is a UUID? Understanding UUID Versions (v1, v4, v5, v7)

What Is a UUID?

A UUID (Universally Unique Identifier)—also referred to as a GUID (Globally Unique Identifier) in Microsoft ecosystems—is a 128-bit number standardized under RFC 4122. UUIDs enable distributed systems to generate unique identifiers independently without central coordination.

UUID String Format

A UUID is represented as 32 hexadecimal digits separated by hyphens into five groups:

xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx
Example: f47ac10b-58cc-4372-a567-0e02b2c3d479

M (digit 13): Specifies the UUID Version (e.g. 4).
N (digit 17): Specifies the RFC 4122 Variant (8, 9, a, or b).

Comparison of UUID Versions

UUID v1: Generated from host MAC address and 60-bit timestamp. (Leaks hardware MAC address).
UUID v4: Generated purely from 122 bits of cryptographic pseudo-randomness. (Most popular).
UUID v5: Generated using SHA-1 hashing over a namespace and name string.
UUID v7: Modern standard encoding a Unix timestamp with random bits for optimal B-Tree database indexing.

Try Related Tools on ToolNest

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Generate cryptographically secure Version 4 (v4) UUIDs and GUIDs using the browser's Web Crypto API. Batch generate single or bulk unique identifiers.

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Convert Unix epoch timestamps (seconds and milliseconds) to human-readable UTC and local date formats, or convert dates into Unix epoch seconds.

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