UUID (Universally Unique Identifier) is a 128-bit identifier represented as 32 hex digits in 5 groups separated by hyphens, e.g. 550e8400-e29b-41d4-a716-446655440000. UUIDs are used as primary keys in databases, file names, session IDs, and more.

What is the difference between UUID v4 and v7?

UUID v4 is fully random. UUID v7 includes a 48-bit Unix timestamp, so UUIDs generated close in time will sort together. v7 is better for database indexes because new UUIDs cluster together instead of being scattered randomly.

Are UUIDs really unique?

The probability of two UUIDv4 values being the same is approximately 1 in 5.3 × 10^36 — effectively zero. You can generate billions of UUIDs and never see a collision.

A Nil UUID is all zeros: 00000000-0000-0000-0000-000000000000. It is a special sentinel value used in some protocols to indicate "no UUID".

UUID Generator (v4, v7, Nil)

Free online UUID generator. Generate UUIDs v4 (random), v7 (time-ordered, sortable), or Nil. Bulk generate up to 500 at once. No signup, 100% browser-based.

UUID Generator

Generate UUIDs (Universally Unique Identifiers) — v4 (random), v7 (time-ordered), Nil. Bulk generate up to 500 at once. Free, no signup.

UUID version

Count

Uppercase

Hyphens (8-4-4-4-12)

How to Use the UUID Generator (v4, v7, Nil)

1Choose the UUID version — v4 random, or timestamp-based where offered.
2Set how many UUIDs you need.
3Click Generate — values come from the browser's cryptographic random source.
4Copy individually or copy all, in uppercase or lowercase, with or without hyphens.