UUID Generator
Generate random UUID v4 identifiers. Generate single or bulk UUIDs with one click.
About UUID Generator
UUIDs (Universally Unique Identifiers) are 128-bit numbers used to uniquely identify resources in distributed systems without requiring a central authority. They are standardized by RFC 4122 and are the preferred identifier format for database primary keys, API request tracking, session management, and distributed system coordination. UUID v4 is the most widely used version, generating identifiers from cryptographically secure random numbers with a collision probability so low that generating 1 billion UUIDs per second for 86 years would still yield only a 50% chance of a single duplicate.
UUID Versions Quick Reference
UUID v1 uses the current timestamp and MAC address, making it time-sortable but potentially exposing hardware information. UUID v3 and v5 generate deterministic IDs from a namespace and name using MD5 and SHA-1 hashing respectively. UUID v4 is purely random and the most commonly used for general-purpose unique identification. UUID v7, introduced in the 2024 update to RFC 9562, combines a Unix timestamp with random bits, providing both uniqueness and natural chronological sorting -- making it ideal for database primary keys where index performance matters.
The UUID format is xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx, where M indicates the version (4 for v4) and N indicates the variant (8, 9, a, or b for RFC 4122). UUIDs can be represented with or without dashes and in uppercase or lowercase. When used as database primary keys, consider UUID v7 or ULID for better index locality compared to random UUID v4. Popular alternatives to UUID include ULID (26-character, Crockford Base32), nanoid (URL-safe, customizable length), and KSUID (K-Sortable Unique ID).
Frequently Asked Questions
What is a UUID?
UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. UUIDs are standardized by RFC 4122 and are commonly used as database primary keys, session tokens, and unique identifiers in distributed systems.
What is UUID v4?
UUID version 4 is generated using random or pseudo-random numbers. It has the format xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx where x is any hex digit and y is one of 8, 9, a, or b. The "4" in the third group indicates version 4.
Can two UUIDs be the same?
Theoretically yes, but practically no. There are 2^122 possible UUID v4 values (about 5.3 x 10^36). The probability of generating duplicate UUIDs is astronomically low — you would need to generate 1 billion UUIDs per second for 86 years to have a 50% chance of a collision.