Are the UUIDs cryptographically random?

Yes. UUID v4 uses the browser crypto.getRandomValues, which is cryptographically secure on all modern browsers.

v4 or v7 — which should I use?

v7 for database primary keys because its timestamp prefix keeps B-tree indexes localized. v4 for everywhere uniqueness matters but ordering does not.

v4 collisions are effectively impossible: 2^122 random bits make duplicates astronomically unlikely.

Generators

Generate RFC 4122 UUID v4 (random) and v7 (time-ordered) identifiers. Bulk generate up to 1000 at a time.

Version

Fully random — suitable for most use cases. Uses crypto.randomUUID().

Count

v4 — Random

122 bits of cryptographically random data. Virtually zero collision probability (2¹²² possible values). The most widely used UUID version.

v7 — Time-ordered

48-bit millisecond timestamp prefix followed by random data. UUIDs sort chronologically, which eliminates B-tree index fragmentation in databases.