🆔 UUID / GUID Generator
Generate UUID v4, v1, NanoIDs, and ULIDs instantly. Single or bulk generation with format options. Click to copy — 100% in-browser using the Web Crypto API.
Frequently Asked Questions
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit ID formatted as 32 hex digits in 8-4-4-4-12 groups. The collision probability is so low they're considered globally unique across all systems and time.
UUID v1 vs v4?
v1 is time-based — embeds the current timestamp and MAC address, making it sortable but potentially revealing system info. v4 is random — 122 bits of cryptographic randomness. Use v4 for most cases where privacy matters.
UUID same as GUID?
Yes. GUID is Microsoft's term for the same concept. They follow the same RFC 4122 standard. Microsoft typically formats them with uppercase and braces: {XXXXXXXX-...}.
What is a ULID?
A ULID (Universally Unique Lexicographically Sortable Identifier) is an alternative to UUID that is sortable by creation time. The first 10 characters encode a millisecond timestamp, the last 16 are random. ULIDs are useful for database primary keys where insertion order matters.
UUID Generator Online — Generate Unique IDs for Databases and APIs
UUIDs are used as primary keys in databases, message IDs in event systems, session tokens, feature flag IDs, and anywhere a unique identifier is needed without a central authority. They're supported natively in PostgreSQL, MySQL 8, MongoDB, and most ORMs.
When to Use UUID vs Sequential IDs
Sequential IDs (1, 2, 3…) are simple but reveal record counts and have contention in distributed systems. UUIDs work well in distributed and microservice architectures where multiple services generate IDs independently. The tradeoff is larger storage (16 bytes vs 4-8 bytes) and slightly worse database index locality.
NanoID vs UUID
NanoID generates shorter URL-safe random IDs (default 21 characters). They have equivalent randomness to UUID v4 with ~30% less space and no dashes, making them ideal for short links, public-facing IDs, and URL parameters.