UUID Generator

A UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 4122. UUIDs are used to uniquely identify information in computer systems. They are globally unique, meaning the same UUID will never be generated twice across different systems. They are commonly used as database primary keys, API identifiers, and distributed system identifiers.

UUID v4 is the most common UUID format. It generates a random identifier using 122 bits of cryptographically secure randomness. The remaining 6 bits are used for version and variant indicators. UUID v4 is the default choice for most applications because of its simplicity and security. With 2^122 possible values, collisions are astronomically unlikely.

UUID v7 (RFC 9562 draft) is a modern UUID format that combines a Unix timestamp in milliseconds (48 bits) with random bits (74 bits). This gives UUIDs time-ordered sortability while maintaining randomness. UUID v7 is ideal for database primary keys and indices because new UUIDs are chronologically sortable, improving B-tree index performance.

Use UUIDs when you need globally unique identifiers across distributed systems, when merging data from multiple databases, when you don't want to expose sequential IDs (security through obscurity), or when you need to generate IDs on the client side. Use auto-increment IDs for simple, single-database applications where performance and readability are priorities.

UUIDs are designed to be universally unique with an extremely high probability of uniqueness. For UUID v4, there are approximately 5.3 × 10^36 possible values — that's 5.3 trillion trillion trillion. While collisions are theoretically possible, the probability is so low that they are practically impossible in normal use. The chance of a collision with 1 billion UUIDs is about 50% only after generating 2.7 × 10^18 UUIDs (birthday problem).

Both UUID v1 and v7 are time-based, but they differ in implementation. UUID v1 uses a 60-bit timestamp in 100-nanosecond intervals since October 15, 1582, plus a node identifier (typically a MAC address). UUID v7 uses a simpler 48-bit Unix timestamp in milliseconds plus random bits. UUID v7 is recommended for modern applications because it's simpler, faster, and avoids privacy concerns associated with MAC address exposure in v1.

Yes! The entire UUID generation process happens in your browser using the Web Crypto API. No internet connection is required after the page loads. All UUIDs are generated locally using cryptographically secure random number generation.