Eazy Toolbox
Skip to tool

UUID Generator

Generate UUIDs in bulk. Version 4 is fully random; version 7 begins with a timestamp so the values sort chronologically. Both use your browser's secure random source.

Your data never leaves your browser. This tool runs entirely on your device.

Generated UUIDs
v4 or v7?
Version 4 is 122 bits of randomness. It is the right default when you simply need an identifier that nobody can guess or predict, and it reveals nothing about when or where it was created.
Version 7 puts a 48-bit millisecond timestamp at the front, followed by randomness. The values therefore sort in creation order, which makes a dramatic difference as a database primary key: random UUIDs scatter inserts across the whole index, while v7 appends to the end like an auto-increment column.
  • Choose v4 for public-facing ids, tokens and anything where creation time must stay private.
  • Choose v7 for database primary keys, event ids and anything you will sort or range-query by time.
How unique are they really?
A version 4 UUID has 122 random bits, giving about 5.3 × 10³⁶ possible values. To reach a 50% chance of a single collision you would need to generate roughly 2.7 × 10¹⁸ of them.
In practice that means collisions are not a risk worth engineering around, provided the generator uses a cryptographic random source. This one uses crypto.getRandomValues, never Math.random.
Privacy
Generation happens entirely in your browser. No values are transmitted or logged, so the identifiers you generate here are yours alone and are never seen by anyone else.
Frequently asked questions
Are these UUIDs safe to use in production?
Yes. They are generated with crypto.getRandomValues, the browser's cryptographically secure random source, and follow RFC 9562 exactly. Nothing is transmitted, so no one else has seen them.
What is the difference between a UUID and a GUID?
Nothing meaningful. GUID is Microsoft's name for the same 128-bit identifier. The two terms are interchangeable, though GUIDs are often written in braces.
Should I use a UUID as a database primary key?
Version 7 is a good choice because it sorts by creation time and keeps index inserts sequential. Version 4 as a clustered primary key causes page splits and index fragmentation, which is why it has a poor reputation for this use.
Can two UUIDs ever be the same?
In theory yes, in practice no. With 122 random bits you would need to generate about 2.7 quintillion v4 UUIDs before reaching a 50% chance of one collision.
Why do all my UUIDs have a 4 in the same position?
That digit is the version field, so every v4 UUID has a 4 there by design. The following character is the variant field and is always 8, 9, a or b. Neither is random.
Related tools