About UUIDs
A UUID (Universally Unique Identifier), sometimes called a GUID, is a 128-bit value written as 32 hexadecimal characters in the pattern 8-4-4-4-12. Its purpose is to let independent systems generate identifiers that will not collide — no central authority, no coordination, just enough randomness that the odds of two machines picking the same value are effectively zero.
This generator produces version 4 UUIDs, the most common kind. Version 4 is generated entirely from random bits, which is what makes it safe to create on a laptop, on a server, inside a database row trigger, or across thousands of microservices all at once. Version 1 and version 7 exist for specific use cases (they embed timestamps), but v4 is the default you should reach for unless you have a reason to pick otherwise.
Each click produces a fresh UUID. The generation happens in your browser using the Web Crypto API, so the values are cryptographically random rather than relying on the weaker Math.random().
How to Generate UUIDs
- Click the generate button to produce a single UUID, or generate a batch of them at once.
- Copy the result to your clipboard with the copy button.
- Keep clicking for as many UUIDs as you need — each one is independent and has no relationship to the others.
Examples
A typical version 4 UUID
Output
3f1a8b7c-9d4e-4a21-8f6b-1e2c3d4e5f60
The 4 at the start of the third group identifies this as version 4. The first character of the fourth group is always 8, 9, a, or b for the DCE variant.
Common Use Cases
- Primary keys in distributed databases where you cannot rely on an auto-incrementing counter.
- Correlation IDs that travel with a request through multiple services for tracing and debugging.
- Idempotency keys on API requests — if the same UUID arrives twice, the server knows to deduplicate.
- File names for user uploads to avoid collisions and to prevent guessable URLs.
- Session tokens or API keys (though for secrets, check that your generator uses a cryptographically secure random source — this one does).
Tips
- UUIDs are long. If you need something shorter, consider UUID v4 encoded as Base58 (26 characters) or a different scheme entirely such as NanoID.
- Because v4 UUIDs are random, they do not sort well as database keys — inserts land all over the index. If you need insert-friendly UUIDs, look at v7, which puts a timestamp at the front.
- Do not embed meaning in a UUID (like hoping to extract a timestamp). A v4 UUID has no embedded information beyond being a distinct value.
Frequently Asked Questions
What is the chance of two UUIDs colliding?
Vanishingly small. To have a 50% chance of a single collision, you would need to generate roughly 2.71 quintillion v4 UUIDs. For practical purposes, treat collisions as impossible.
What is the difference between a UUID and a GUID?
They are the same thing. GUID is Microsoft's preferred name; UUID is the name used in the RFC. The format and guarantees are identical.
Should I use UUID v4 or v7?
v4 is the default and safe choice. v7 is newer and places a timestamp at the front, which improves insert performance in databases that cluster rows by primary key. If you are choosing a new scheme today and your platform supports it, v7 is worth considering.
Are these generated UUIDs stored anywhere?
No. The tool runs in your browser. Generated values are not sent to any server or saved between sessions.