UUID v4 Generator Online — Free Unique Identifiers

How it works

A UUID (Universally Unique Identifier) version 4 is a 128-bit identifier represented as 32 hexadecimal characters split into 5 groups (format 8-4-4-4-12). Of those 128 bits, 122 are random; the remaining 6 are fixed to indicate the UUID's version (4) and variant, following the RFC 4122 standard.

The reason they're used in distributed systems, instead of simple incremental IDs (1, 2, 3...), is that they allow generating unique identifiers in a fully decentralized way: two different services, without communicating with each other, can each generate millions of UUIDs with no practical risk of collision.

This generator uses crypto.randomUUID(), the browser's native API introduced specifically for this purpose, which internally uses the same cryptographic entropy source as every other generator on this site. The collision probability between two generated v4 UUIDs is roughly 1 in 5.3×10³⁶ — to have a 50% chance of a single collision, you'd need to generate more than 2.7 billion UUIDs per second for 100 years.

UUID versions per the RFC 4122 standard

What is it for?

• ✓Generating unique IDs for database records
• ✓Creating tokens for APIs and authentication systems
• ✓Identifiers for objects in web applications
• ✓Unique names for uploaded files or resources
• ✓Testing and mock data for distributed systems
• ✓Primary keys in NoSQL or distributed databases
• ✓Session or transaction identifiers in backend systems
• ✓Generating unique reference IDs for tickets or orders

Frequently asked questions

What is a UUID v4?

A UUID v4 is a 128-bit unique identifier in standard format (e.g. 550e8400-e29b-41d4-a716-446655440000). The "v4" means it's randomly generated, following the RFC 4122 standard.

Can two generated UUIDs collide?

The collision probability is astronomically small (1 in 5.3×10³⁶). In practice, every generated UUID is unique for any real application.

How is the UUID generated?

We use crypto.randomUUID(), a native browser API that generates cryptographically secure UUIDs without sending any data to a server.

What does the 8-4-4-4-12 format mean?

It's the standard way of representing the UUID's 32 hexadecimal characters, separated by hyphens in groups of 8, 4, 4, 4 and 12 characters, per the RFC 4122 standard.

Why use a UUID instead of an incremental numeric ID?

UUIDs allow decentralized generation without coordination between systems — useful in distributed databases, microservices, or when you need to generate IDs client-side before saving to the server.

Are the UUIDs generated here valid for production?

Yes, they follow the RFC 4122 version 4 standard and are generated with the same cryptographic API browsers use for other security operations, so they're suitable for use in real systems.