Generate UUID v4 identifiers in bulk. Copy single or multiple UUIDs instantly. Free online developer tool. This tool runs entirely in your browser — no data is sent to any server. It's fast, free, and works on any device.
A UUID (Universally Unique Identifier) is a 128-bit label used to identify information in computer systems without central coordination. The most common form, UUID v4, is randomly generated and has a collision probability so astronomically low that for all practical purposes, every generated UUID is guaranteed to be unique. Formatted as 32 hexadecimal digits in 8-4-4-4-12 groupings (e.g., 550e8400-e29b-41d4-a716-446655440000), UUIDs are used as primary keys in distributed databases, API request IDs, session tokens, file names, correlation IDs in logging, and anywhere a unique identifier is needed without coordination between systems.
UUID v1 uses a timestamp and MAC address (not fully random, privacy concerns). UUID v3 and v5 are namespace-based (deterministic). UUID v4 is random and the most widely used. UUID v7 (newer) is time-ordered for better database index performance.
UUID v4 generates 2^122 possible values — roughly 5.3 × 10^36. The probability of generating a duplicate in 1 trillion UUIDs is about 1 in 10^18. For all practical purposes, treat them as unique.
UUID v4 works but has poor index performance in traditional B-tree indexes due to randomness causing page splits. UUID v7 or ULID are better choices for database keys as they're time-ordered.
They're the same thing. GUID (Globally Unique Identifier) is Microsoft's name for UUID. They follow the same RFC 4122 standard and are fully compatible.
Yes! UUID v4 requires only a source of randomness (your browser's crypto.getRandomValues()), not internet access. This tool works fully offline after the page loads.