Should I use v4 or v7?

v4 for anything where the identifier is just an identifier. v7 when it becomes a database primary key and you care about index locality, or when sorting by id should mean sorting by creation time.

Can two UUIDs collide?

In practice, no. A v4 UUID has 122 random bits; you would need to generate billions per second for decades before a collision became likely. The real risk is a weak random source, which is why this uses the browser's cryptographic one.

Does v7 leak information?

Yes, by design — the creation time is embedded and readable by anyone holding the identifier. That is fine for a database key and wrong for anything that should not reveal when it was made. Use v4 there.

Are these generated on your server?

There is no server involved. They are generated in your browser and never transmitted, so nobody else has ever seen the values you take from this page.

What is the nil UUID for?

It is all zeroes and serves as an explicit “no identifier” placeholder, in the same spirit as a null — useful when a field requires a UUID but the value is genuinely absent.

UUID Generator

Generate v4 or v7 UUIDs from your browser's crypto source.

Everything runs inside your browser. Your files never leave your device.

Result

The result appears here as you type.

Ask about UUID Generator

Questions about what this tool does, which option to pick, or what it can and cannot handle.

This is the one part of the site that uses a server. The question you type here is sent to an AI provider to be answered — your files and whatever you put in the tool above are not, and the assistant cannot see them. Answers are generated and can be wrong; the tool itself is not guessing.

About the UUID Generator

A UUID is 128 bits formatted as thirty-two hexadecimal digits in five hyphenated groups, and its point is that you can generate one anywhere, at any time, without coordinating with anything, and be confident it has never been generated before.

Version 4 is almost entirely random and is the right default for most uses. Version 7 is more interesting if the identifier is going into a database. It puts the creation time in the leading 48 bits, so v7 identifiers sort chronologically as plain strings — which means that as a primary key they append to the end of an index rather than scattering writes across it, the way random v4 keys do. On a busy table that difference is measurable.

The generator here produces v7 correctly, which not all of them do. Identifiers created within the same millisecond share a timestamp, so a monotonic counter occupies the twelve bits after the version nibble. Without it, a batch generated in one tick would be ordered only by its random tail, and the single property v7 exists to provide would be quietly missing.

All randomness comes from your browser's cryptographic random source, not from a general-purpose pseudo-random function. Nothing is generated on a server, so no identifier you take from this page has ever existed anywhere else.

How to use it

1Choose the version: v4 for general use, v7 if the identifier is going into a database as a key.
2Set how many you need — up to a thousand at a time.
3Adjust the formatting: uppercase, braces, or hyphens removed.
4Copy the list, or download it as a text file.

Questions

Should I use v4 or v7?: v4 for anything where the identifier is just an identifier. v7 when it becomes a database primary key and you care about index locality, or when sorting by id should mean sorting by creation time.
Can two UUIDs collide?: In practice, no. A v4 UUID has 122 random bits; you would need to generate billions per second for decades before a collision became likely. The real risk is a weak random source, which is why this uses the browser's cryptographic one.
Does v7 leak information?: Yes, by design — the creation time is embedded and readable by anyone holding the identifier. That is fine for a database key and wrong for anything that should not reveal when it was made. Use v4 there.
Are these generated on your server?: There is no server involved. They are generated in your browser and never transmitted, so nobody else has ever seen the values you take from this page.
What is the nil UUID for?: It is all zeroes and serves as an explicit “no identifier” placeholder, in the same spirit as a null — useful when a field requires a UUID but the value is genuinely absent.