Question 1

What is a UUID?

Accepted Answer

A UUID (Universally Unique Identifier) is a 128-bit identifier represented as 32 hex digits separated by hyphens, e.g. '550e8400-e29b-41d4-a716-446655440000'. UUIDs are designed to be globally unique without coordination between systems, making them ideal for database primary keys, distributed systems, and file names.

Question 2

What is UUID version 4?

Accepted Answer

UUID v4 uses random numbers for all bits except the version (4) and variant (10xx) bits. This makes v4 UUIDs unique through randomness rather than MAC address or timestamp. Toolhub uses the browser's crypto.getRandomValues(), which is cryptographically secure — far better than Math.random().

Question 3

Are UUID v4 collisions possible?

Accepted Answer

Theoretically yes, practically no. With 122 bits of randomness, you'd need to generate 2.71 × 10^18 UUIDs to have a 50% chance of one collision. For comparison, generating 1 billion UUIDs per second for 85 years gives a 50% collision probability. UUID v4 is safe for any practical use case.

Question 4

What's the difference between UUID and GUID?

Accepted Answer

None — UUID and GUID refer to the same thing. UUID is the RFC 4122 standard name; GUID is Microsoft's name for the same format. The two terms are interchangeable. Some Microsoft tools wrap UUIDs in braces '{...}' but the underlying format is identical.

UUID Generator — RFC 4122 v4

UUID Generator

How to use this tool

Frequently Asked Questions

UUID Generator

How to use this tool

Frequently Asked Questions

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