UUID Generator – Random Version 4 UUIDs
About UUID Generator
Generate random version 4 UUIDs — one at a time or up to fifty at once — with optional uppercase output and the hyphens removed if your format needs them gone.
A UUID is a 128-bit identifier designed to be unique without any central authority handing out numbers. That is what makes it useful in distributed systems: two machines can each mint an identifier with no coordination and no realistic chance of collision.
Version 4 UUIDs are almost entirely random, which is what you want for a general-purpose identifier. These are generated with the browser's cryptographic random source, so they are properly unpredictable rather than derived from a weak pseudo-random function.
What you can use it for
- Create a primary key for a database row before it is inserted.
- Generate correlation or request IDs for tracing across services.
- Produce test fixtures that need unique identifiers.
- Create an idempotency key for an API call.
- Generate a batch of unique identifiers for a seed script or spreadsheet.
How it works, step by step
- 1
Choose how many
Generate a single UUID or up to fifty in one go.
- 2
Set the format
Toggle uppercase, and remove hyphens if your target format requires it.
- 3
Copy what you need
Copy an individual UUID, or all of them at once.
- 4
Generate again
Each generation produces a fresh set.
Frequently asked questions
What is a version 4 UUID?
A UUID whose bits are randomly generated, apart from a few reserved to mark the version and variant. It is the standard choice when you simply need a unique identifier with no embedded meaning.
Can two UUIDs ever collide?
In theory yes, in practice no. A version 4 UUID has 122 random bits — you would need to generate billions per second for many years before a collision became likely.
Are these cryptographically random?
Yes. They use the browser's secure random source rather than an ordinary pseudo-random function, so they are not predictable from earlier values.
Should I use a UUID as a database primary key?
It is common and works well, especially when records are created across several services. The trade-off is that random UUIDs index less efficiently than sequential integers on large tables — some teams use time-ordered variants for that reason.
Is a UUID a secret?
Treat it as an identifier, not a credential. A random UUID is hard to guess, but it is often logged and passed around, so it should not be the only thing protecting access to something.