A UUID (Universally Unique Identifier) is a 128-bit value used to identify something, like a database row or a session, without needing a central authority to hand out IDs. The odds of two randomly generated UUIDs colliding are astronomically small.

What's the difference between v1, v4, and v7?

v4 is fully random and the most common choice for general use. v1 is time-based and includes a randomly generated node identifier instead of a real MAC address. v7 is also time-ordered but places the timestamp at the front, so v7 UUIDs sort chronologically and work well as database primary keys.

Why would I use v7 instead of v4 for a database key?

Because v7's timestamp prefix means new rows insert in roughly sequential order, which is friendlier to database indexes than the fully random ordering of v4. It still keeps the rest of the value random and unpredictable.

Does v1 expose my real MAC address?

No. The node identifier is generated randomly for each UUID, with the multicast bit set to mark it as not a real IEEE 802 address, exactly as RFC 4122 recommends when a genuine hardware address isn't used.

Is my data stored anywhere?

No. UUIDs are generated on request and are not logged or saved, since there is nothing about them worth retaining beyond the response.

DAILYTOOLER

UUID generator

Generate UUIDs (v1, v4, v7) in bulk, with options for uppercase and hyphens.

Version

Count

Uppercase

With hyphens

Generated UUIDs

What is a UUID generator?

Generate one or many UUIDs at once, in version 1 (time-based), version 4 (random), or version 7 (time-ordered) format. Toggle uppercase and hyphens freely; they just reformat the batch you already generated instead of creating new ones.

Useful for seeding test data, generating database keys, or creating unique identifiers for anything that needs one.

Need one GUID in lots of different formats instead, like C#, SQL, or braces? Try the GUID formatter.

UUID generator

What is a UUID generator?

Frequently asked questions