UUID generator

How to make a UUID

1. Choose how many UUIDs you need, from 1 to 1,000.
2. Turn on upper case or remove hyphens if your system expects that format.
3. Generate the list.
4. Copy them all, one per line.

What a UUID looks like

A UUID (universally unique identifier) is a 128 bit number written as 32 hexadecimal characters in five groups separated by hyphens, in the pattern 8-4-4-4-12. That makes 36 characters in total, for example 3f2504e0-4f89-41d3-9a0c-0305e82c3301.

Two positions carry fixed meaning in a version 4 UUID:

• The first character of the third group is always 4, which marks it as version 4 (random)
• The first character of the fourth group is always 8, 9, a or b, which marks the standard variant

The remaining 122 bits are random. This tool creates them with crypto.randomUUID, the browser's built in generator backed by a cryptographic random source, so nothing comes from or goes to a server.

Could two UUIDs ever match?

In theory yes, in practice no. With 122 random bits there are more than 5 x 10^36 possible version 4 UUIDs. You would need to generate around 2.7 quintillion of them before there was even a 50 percent chance of a single duplicate. For databases, file names, order references and test data, you can treat each one as unique.

The thing that does cause duplicates is human error, such as copying the same UUID into two records, so generate a fresh one each time rather than reusing a list.

UUID or GUID

They are the same thing. GUID (globally unique identifier) is the name Microsoft uses in Windows, .NET and SQL Server. Microsoft tools often show GUIDs in upper case, sometimes inside curly braces, while most other systems use lower case. Case does not change the value, which is why this tool offers an upper case option.

Questions people ask