Are v4 UUIDs really unique?

With 122 bits of entropy from crypto.getRandomValues, you can generate 2^61 UUIDs before reaching a 50% collision probability. For practical purposes they are unique.

Should I use v4 or v7?

For new systems, v7. Its monotonic time prefix makes database B-tree indexes efficient without giving up uniqueness. Use v4 only when you explicitly do not want the creation time to be recoverable.

Is the Nil UUID useful?

It is a fixed constant (00000000-0000-0000-0000-000000000000) used as a placeholder or sentinel in systems that require a UUID-typed field.

UUID Generator

Generate cryptographically random v4 UUIDs or time-sortable v7 UUIDs, one at a time or in bulk.

Version

Count (1–1000)

Casing

Using crypto.getRandomValues — 122 bits of entropy per v4.

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