Can two generated UUIDs ever be the same?

In theory, yes; in practice, no. A v4 UUID has 122 random bits, so you'd need to generate about a billion IDs per second for about 86 years to reach a 50% chance of one collision.

Is a GUID the same as a UUID?

Yes. GUID is Microsoft's name for the same format. Windows tools often show them in uppercase with braces, which you can turn on above.

Does a v7 UUID reveal when it was created?

Yes, the first 48 bits are a Unix timestamp in milliseconds. If creation time is sensitive, use v4.

Free developer tool

UUID Generator (v4 and v7)

Generate up to 1,000 random v4 or time-ordered v7 UUIDs at once, and inspect any UUID's version and timestamp.

Version

How manymax 1,000

UppercaseHyphens{Braces}

0 UUIDs

Inspect a UUIDversion, variant, embedded time

Version 4 or version 7?

Both are 128-bit unique identifiers defined in RFC 9562. Version 4 is fully random, the most common choice. Version 7 starts with a millisecond timestamp, so new IDs sort after old ones. That keeps database indexes compact and fast, which is why v7 is becoming the default for primary keys.

IDs are generated in your browser with the Web Crypto secure random source. In bulk v7 batches, IDs created in the same millisecond use a counter so the list stays in creation order.

Inspect any UUID

Paste a UUID into the inspector to see its version, variant and, for v1, v6 and v7, the moment it was created.

Frequently asked questions

Can two generated UUIDs ever be the same?: In theory, yes; in practice, no. A v4 UUID has 122 random bits, so you'd need to generate about a billion IDs per second for about 86 years to reach a 50% chance of one collision.
Is a GUID the same as a UUID?: Yes. GUID is Microsoft's name for the same format. Windows tools often show them in uppercase with braces, which you can turn on above.
Does a v7 UUID reveal when it was created?: Yes, the first 48 bits are a Unix timestamp in milliseconds. If creation time is sensitive, use v4.