Orpheus

UUID Generator

Cryptographically random v4 UUIDs, as many as you need.

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Every tool runs entirely in your browser. Your files are never uploaded to a server.

A UUID is a 128-bit identifier designed to be unique without any central coordination. Version 4 is 122 random bits, so two independently generated values colliding is effectively impossible in practice.

How to use UUID Generator

  1. Choose how many. One, or up to five hundred at a time.
  2. Pick a format. Lowercase is standard; braced and compact suit particular systems.
  3. Copy them. Generated locally using the browser’s cryptographic random source.

About generating UUIDs

UUIDs solve a specific problem: producing identifiers that will not collide when several systems generate them independently, with no coordination between them. That is why they are 128 bits and why they look unwieldy — the size is what buys the guarantee. Version 4, the common one, sets six bits to identify the version and variant and fills the remaining 122 with randomness. The collision arithmetic is genuinely reassuring: to reach even a one-in-a-billion chance of a duplicate you need to generate on the order of a hundred billion of them. The practical risks are elsewhere. A poor random source turns the guarantee into a hope, which is why generating them with a general-purpose random function rather than a cryptographic one is a real bug rather than a pedantic one. And using a random UUID as a clustered primary key has a well-documented performance cost, because each insert lands at a random point in the index rather than at the end, fragmenting pages and inflating writes. UUIDv7, standardised in 2024, encodes a timestamp in the leading bits so values sort roughly by creation time while remaining unique — which is why new systems increasingly choose it over v4 for storage while keeping v4 for anything that should not be guessable or ordered.

Frequently asked questions

Can two UUIDs ever be the same?
In theory yes, in practice no. Version 4 has 122 random bits, so you would need to generate about a billion a second for 85 years to reach a 50 percent chance of one collision. The real risk is a weak random source, not the format.
Are these generated on your server?
No. They come from crypto.randomUUID in your own browser, which uses the operating system’s cryptographic random source. A UUID generated on someone else’s server and sent to you has been seen by that server, which defeats the point for anything security-adjacent.
Should I use a UUID as a database primary key?
It depends on the database. Random UUIDs scatter inserts across the index, which fragments B-trees and hurts write performance at scale. UUIDv7, which is time-ordered, was standardised specifically to fix that, and many systems now prefer it or a sequential ID.
What do the version and variant digits mean?
The first character of the third group is the version — 4 here — and the first character of the fourth group encodes the variant, which is why it is always 8, 9, a or b. Only 122 of the 128 bits are random; those six are fixed.

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