UUID v4 Generator
Cryptographically random UUIDs — generate up to 20 at once.
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit label presented as 32 hexadecimal digits in five groups separated by hyphens: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. The version 4 variant is randomly generated, making it statistically impossible to collide with another UUID. There are 2¹²² possible UUID v4 values — enough that even generating a billion per second for billions of years would not produce a collision.
Common uses for UUIDs
UUIDs are used as primary keys in databases, unique identifiers for records in distributed systems, file names for uploaded assets, session tokens, API keys, and correlation IDs in logging. Unlike sequential integers, UUIDs can be generated on the client side without coordination with a server, making them ideal for offline-first applications.
Frequently asked questions
Is UUID the same as GUID?
GUID (Globally Unique Identifier) is Microsoft's term for the same concept. GUIDs and UUIDs follow the same RFC 4122 format and are interchangeable in most contexts, although GUIDs are sometimes displayed in uppercase with curly braces.
Are these UUIDs truly unique?
Yes. They use crypto.getRandomValues (the same secure random source used for cryptographic operations) to fill 122 bits of randomness. The probability of two UUIDs colliding is astronomically small — effectively zero for any practical application.
What do the specific bits in UUID v4 mean?
The 13th hex digit (in the third group) is always 4, indicating version 4. The 17th hex digit (first of the fourth group) is either 8, 9, a, or b, indicating the variant. The remaining 122 bits are cryptographically random.
