Generate RFC 4122-compliant UUIDs — v1 (time-based), v4 (random), v5 (namespace + SHA-1), or Nil UUID. Bulk generation and multiple output formats supported.
A UUID (Universally Unique Identifier) is a 128-bit label defined by RFC 4122. The standard defines five versions, each using a different strategy to guarantee uniqueness. UUIDs are the foundation of distributed system identity — from database primary keys to transaction correlation IDs and OAuth state parameters.
Combines the current timestamp (60-bit, 100ns intervals since Oct 1582) with the host's MAC address. Sortable by creation time, but exposes the machine's MAC which may be a privacy concern.
Uses 122 random bits. No coordination between generators needed. Collision probability is 1 in 5.3×10³⁶ — effectively zero. The most widely used version for databases and distributed systems.
Deterministic: same namespace + name always produces the same UUID. Uses SHA-1 internally. Ideal for generating stable IDs from content (URLs, email addresses, domain names).
All 128 bits are zero: 00000000-0000-0000-0000-000000000000. Used as a sentinel value in databases and APIs to represent "no UUID" or an unset foreign key.