What's the difference between v4 and v7?

v4 is fully random. v7 prepends a millisecond timestamp so IDs sort chronologically, which is friendlier to database indexes.

What is a UUID (or GUID)?

A UUID (Universally Unique Identifier), also called a GUID on Microsoft platforms, is a 128-bit value written as 32 hex digits in five hyphen-separated groups. It identifies something uniquely without a central authority handing out numbers.

Are UUIDs guaranteed to be unique?

Not guaranteed, but collisions are astronomically unlikely. A v4 UUID has 122 random bits, so you would need to generate billions per second for many years before a clash became probable.

Are these generated offline?

Yes. IDs are created in your browser with window.crypto, so nothing is requested from a server and nothing you generate is logged.

Does a v7 UUID reveal when it was created?

Yes. v7 embeds a millisecond timestamp, so the creation time is recoverable from the ID. Use v4 if you need the value to leak nothing about timing.

UUID Generator

Generate v4 (random) or v7 (time-ordered) UUIDs in bulk.

Settings

Version

v4 vs v7

v4: 122 random bits. The classic UUID; supported everywhere; no order.

v7: first 48 bits are a Unix-millisecond timestamp, the rest random. Sortable by creation time.

v7 is much friendlier to B-tree indexes (Postgres, MySQL): inserts hit the rightmost page instead of scattering writes across the index. Use v7 unless you specifically need unguessable IDs.

Random. Universally supported.

Time-ordered. Friendlier to databases.

How many

1 to 1,000 at a time.

Format

Hyphens

Uppercase

Wrap in braces { }

Output ()

The URL below carries every option. Open it to generate fresh UUIDs with the same settings.

Some inputs are too long to fit in the URL.

Share URL

Anyone with this link can read the values it contains. Do not use it for sensitive data.

How to use the UUID Generator

Pick UUID v4 or v7.
Choose how many to generate.
Copy or download the list.

Frequently asked questions

What's the difference between v4 and v7?: v4 is fully random. v7 prepends a millisecond timestamp so IDs sort chronologically, which is friendlier to database indexes.
What is a UUID (or GUID)?: A UUID (Universally Unique Identifier), also called a GUID on Microsoft platforms, is a 128-bit value written as 32 hex digits in five hyphen-separated groups. It identifies something uniquely without a central authority handing out numbers.
Are UUIDs guaranteed to be unique?: Not guaranteed, but collisions are astronomically unlikely. A v4 UUID has 122 random bits, so you would need to generate billions per second for many years before a clash became probable.
Are these generated offline?: Yes. IDs are created in your browser with window.crypto, so nothing is requested from a server and nothing you generate is logged.
Does a v7 UUID reveal when it was created?: Yes. v7 embeds a millisecond timestamp, so the creation time is recoverable from the ID. Use v4 if you need the value to leak nothing about timing.