A Universally Unique Identifier is a 128-bit value written as 36 characters: 8-4-4-4-12 hex digits, like 550e8400-e29b-41d4-a716-446655440000. Its point is that anyone can generate one anywhere, with no central registry, and be practically certain it has never been used before.

What does “version 4” mean?

UUID versions describe how the value was made. Version 4 is the random one: 122 of its 128 bits come straight from a cryptographically secure random generator (the remaining 6 bits mark the version and variant). It’s the most widely used version for IDs in databases and APIs.

Can two UUIDs ever collide?

In theory yes, in practice no. There are about 5.3 × 10³⁶ possible v4 UUIDs. You would need to generate roughly a billion UUIDs per second for about 85 years to reach even a 50% chance of a single collision. Systems worldwide rely on this math.

How random is this generator?

It uses your browser’s built-in cryptographically secure random source (crypto.randomUUID, with crypto.getRandomValues as fallback) — the same quality of randomness used for encryption keys. It never uses Math.random(), which would be predictable.

Are the UUIDs generated on a server? Could anyone see them?

No — they are generated locally in your browser and never transmitted anywhere. Nothing is stored or logged, and the page works offline. The IDs you generate here exist only on your screen until you copy them.

What are UUIDs used for?

Database primary keys (especially across distributed systems where auto-increment numbers would clash), request and correlation IDs in logs, file names, API keys’ public parts, order references — anywhere you need an ID without coordinating who assigns it.

Should I use the uppercase or no-hyphens options?

The RFC canonical form is lowercase with hyphens — use that unless a system demands otherwise. Some databases and legacy APIs store UUIDs as 32 hex characters without hyphens, and some Windows tooling shows them uppercase; the toggles exist for exactly those cases.

UUID Generator

Generate one or thousands of random version-4 UUIDs from your browser’s secure random generator.

Files never leave your device Instant — no upload waitFree, no sign-up

How many?

UppercaseRemove hyphens

Generate v4 UUIDs — one or a thousand, cryptographically random

Need an ID that’s guaranteed unique without asking anyone? That’s what a UUID is for. This free generator produces version-4 (random) UUIDs using your browser’s cryptographically secure random source — one appears the moment the page loads, and you can generate up to 1,000 at once for test data, database seeding or import files.

Real randomness, generated locally

Every UUID here comes from the same secure randomness your browser uses for cryptography — not a predictable pseudo-random function, and not a server. IDs are generated on your device, never transmitted, never logged. For identifiers that may end up naming private records, that’s the only sensible arrangement.

Formats for every system

The canonical form is lowercase with hyphens — but real systems disagree, so there are toggles forUPPERCASE and hyphen-free (32-character) output, applied instantly to the whole batch. Copy everything with one click, or download large batches as a .txt file, one UUID per line — ready for scripts and spreadsheet imports.

Why v4 collisions aren’t worth worrying about

A v4 UUID carries 122 random bits — about 5.3 × 10³⁶ possibilities. Generating a billion per second, you’d wait decades for a 50/50 chance of one duplicate. This is why UUIDs are the default distributed-systems ID: uniqueness by mathematics instead of coordination.

Related free tools

Need a deterministic fingerprint of existing data instead of a random ID? Use thehash generator. Stamping records with time? TheUnix timestamp converter translates between dates and epoch seconds. Making readable URL identifiers? Try the slug generator.

Frequently Asked Questions

What is a UUID?
A Universally Unique Identifier is a 128-bit value written as 36 characters: 8-4-4-4-12 hex digits, like 550e8400-e29b-41d4-a716-446655440000. Its point is that anyone can generate one anywhere, with no central registry, and be practically certain it has never been used before.
What does “version 4” mean?
UUID versions describe how the value was made. Version 4 is the random one: 122 of its 128 bits come straight from a cryptographically secure random generator (the remaining 6 bits mark the version and variant). It’s the most widely used version for IDs in databases and APIs.
Can two UUIDs ever collide?
In theory yes, in practice no. There are about 5.3 × 10³⁶ possible v4 UUIDs. You would need to generate roughly a billion UUIDs per second for about 85 years to reach even a 50% chance of a single collision. Systems worldwide rely on this math.
How random is this generator?
It uses your browser’s built-in cryptographically secure random source (crypto.randomUUID, with crypto.getRandomValues as fallback) — the same quality of randomness used for encryption keys. It never uses Math.random(), which would be predictable.
Are the UUIDs generated on a server? Could anyone see them?
No — they are generated locally in your browser and never transmitted anywhere. Nothing is stored or logged, and the page works offline. The IDs you generate here exist only on your screen until you copy them.
What are UUIDs used for?
Database primary keys (especially across distributed systems where auto-increment numbers would clash), request and correlation IDs in logs, file names, API keys’ public parts, order references — anywhere you need an ID without coordinating who assigns it.
Should I use the uppercase or no-hyphens options?
The RFC canonical form is lowercase with hyphens — use that unless a system demands otherwise. Some databases and legacy APIs store UUIDs as 32 hex characters without hyphens, and some Windows tooling shows them uppercase; the toggles exist for exactly those cases.