UUID Generator Online

UUIDs (Universally Unique Identifiers) are 128-bit identifiers formatted as xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx — 32 hex characters in five groups separated by hyphens. They're used as database primary keys, session tokens, correlation IDs, and anywhere you need a unique ID that doesn't require a central authority to assign it.

How it works

This tool generates Version 4 UUIDs, which are randomly generated. Version 4 UUIDs set specific bits to indicate the version and variant, and fill the remaining 122 bits with random data from crypto.getRandomValues() — the browser's cryptographically secure random number generator. Your UUIDs are generated locally and never sent to a server.

How to use it

1. Click Generate UUID to create a new UUID
2. Click Generate Batch to generate multiple at once (useful when you need to pre-populate test data)
3. Click any UUID to copy it to your clipboard

A few things worth knowing

• Collision probability is negligible: With 122 bits of random data per UUID, you'd need to generate approximately 2.7 quintillion UUIDs before having a 50% chance of a collision. For all practical purposes, they're unique
• Version 4 vs other versions: Version 1 UUIDs encode the MAC address and timestamp (privacy concern). Version 5 uses SHA-1 hashing of a namespace and name. Version 4 is purely random and the most widely used
• Case doesn't matter: 6ba7b810-9dad-11d1-80b4-00c04fd430c8 and its uppercase equivalent are the same UUID. Many systems normalise to lowercase
• Not sortable by time: Unlike Version 7 UUIDs or ULIDs, Version 4 UUIDs are not time-ordered. If you need sortable IDs, look into ULID or UUIDv7

FAQ

Are UUIDs truly unique? Not mathematically guaranteed — theoretically two random UUIDs could match. In practice, the probability is so low (roughly the same as winning the lottery 5 times in a row) that they're treated as universally unique in all real systems.

Can I use UUIDs as database primary keys? Yes, and it's common. The main trade-off vs auto-incrementing integers is index fragmentation (random values create non-sequential inserts, which can affect B-tree performance at scale) but the benefits (distributed generation, no ID exposure) often outweigh this.

What does crypto.getRandomValues() mean? It's the browser's API for generating cryptographically secure random bytes — suitable for security-sensitive use, unlike Math.random().

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