UUID Generator

Generate UUIDs in your browser — v1, v4, or v7, in bulk, with format options. All generation happens locally; nothing is sent to any server.

Quick:
1 UUID generated

Inspect a UUID

Paste any UUID below to decode its version, variant, and — for v1 and v7 — its embedded timestamp.

UUID reference

Format

A UUID is 128 bits represented as 32 hex digits split into 5 groups by hyphens:

xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx
  • M — version digit (1–8)
  • N — variant bits (8, 9, a, or b for RFC 4122)
  • Groups: 8-4-4-4-12 hex characters

Versions

  • v1 — Gregorian timestamp + MAC address (simulated here with random node)
  • v2 — DCE Security (rarely used)
  • v3 — MD5 hash of namespace + name
  • v4 — Fully random; most widely used
  • v5 — SHA-1 hash of namespace + name
  • v6 — Reordered v1 for better DB sorting
  • v7 — Unix millisecond timestamp + random; sortable and modern
  • v8 — Custom/vendor-defined

Collision probability

For v4, the odds of generating a duplicate UUID are astronomically low. To have a 50% chance of a single collision you would need to generate ~2.7 × 1018 UUIDs. In practice, collisions are not a concern.

v7 is slightly less random (48 bits are reserved for the timestamp) but still provides ~74 random bits — more than enough for any application.

When to use which

  • v4 — Default choice. Session tokens, request IDs, entity IDs when ordering doesn't matter.
  • v7 — Database primary keys. Timestamp prefix allows index-friendly ordering without a separate created_at column.
  • v1 — Legacy systems, log correlation where the timestamp embedded in the ID is useful.
  • Nil — Placeholder / zero value in APIs and databases.