UUID Generator
Generate random RFC 4122 version 4 UUIDs in bulk.
Why use this tool?
Generate random version 4 UUIDs (GUIDs) for database IDs, test data and API keys, using the browser's secure random generator.
How to use it
- Choose how many (1-100).
- Click Generate.
- Copy them all.
What a version 4 UUID is
A UUID (universally unique identifier, called GUID in Microsoft tools) is a 128-bit value written as 32 hexadecimal digits in five groups, like 3f2b8c1e-7a4d-4e9b-9c2a-5d1e8f6a7b30. Version 4 UUIDs are random: 122 of the 128 bits come from a random generator, and the rest mark the version (the 4 at the start of the third group) and the variant.
This tool uses your browser's crypto.randomUUID(), which draws from the operating system's cryptographically secure random source. You can generate from 1 to 100 at a time.
Will two ever collide?
With 122 random bits there are about 5.3 × 10^36 possible values. You would need to generate roughly 2.7 quintillion (2.7 × 10^18) UUIDs to have a 50% chance of a single duplicate. For any real application, treating them as unique is safe, which is why they can be created independently on many machines without coordination.
That property is the main reason to use them: a client, a mobile app offline, or several servers can each create IDs that won't clash when the records are merged later.
Choosing an ID type
UUIDs are good primary keys for distributed systems and for IDs that appear in URLs, because they don't reveal how many records exist or allow guessing the next one, unlike sequential numbers (order 1001, 1002...).
Their randomness has a cost in databases: random keys scatter inserts across an index, which can slow down very large tables. Newer time-ordered formats such as UUID version 7 address this; if you're designing a high-volume table, consider them. Also note that a UUID is an identifier, not a secret. Don't use one as a password or as the only protection on a private link.
Frequently asked questions
Are UUID and GUID the same thing?
Yes. GUID is Microsoft's name for the same 128-bit identifier format.
Can two generated UUIDs be the same?
In theory yes, in practice no: you'd need billions of billions of them before a duplicate became likely.
Are these UUIDs secure enough for tokens?
They come from a secure random source, but tokens should be designed as secrets with enough length and an expiry. Use a dedicated token or password generator for that.