UUID Generator

What a UUID is

A UUID (universally unique identifier), also called a GUID, is a 128-bit value written as 32 hexadecimal digits in five groups, for example 3fa85f64-5717-4562-b3fc-2c963f66afa6. UUIDs let separate systems create identifiers independently, with no central counter, and still be practically certain they will never clash.

Version 4: random UUIDs

This tool generates version 4 UUIDs, where 122 of the 128 bits are random. The remaining bits mark the version and variant, which is why every v4 UUID has a 4 at the start of the third group. Values come from your browser's cryptographically secure generator (crypto.randomUUID), not from Math.random.

How unique is unique? You would need to generate about a billion UUIDs every second for roughly 85 years before the chance of a single duplicate reached 50%.

Where developers use them

• Primary keys in databases, especially distributed ones or where IDs are created on the client.
• Idempotency keys for payment and API requests, so a retried request is not processed twice.
• Correlation IDs to trace one request through logs across services.
• File names for uploads, so names never collide.
• Test fixtures and seed data.

Things to consider

• Random UUIDs do not sort by creation time, which can slow down inserts into some database indexes. Time-ordered formats such as UUID v7 address that.
• UUIDs are hard to guess but are not secrets. Do not use them as passwords or access tokens on their own.