UUID Generator

What is a UUID (or GUID)?

A UUID (Universally Unique Identifier), often called a GUID (Globally Unique Identifier) in Microsoft ecosystems, is a 128-bit identifier designed to be globally unique without central coordination. The current standard is RFC 9562, which replaced RFC 4122. Correctly generated UUIDs can still collide, but the probability is extraordinarily small.

How to Generate a Random UUID v4

This tool generates Version 4 UUIDs using cryptographically secure random numbers. A v4 UUID has the format xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where the 4 identifies the version and y is one of 8, 9, a, or b. UUID v4 contains 122 random bits, giving 2^122 possible random values. Roughly 2.7 quintillion randomly generated UUIDs would be needed for the collision probability to reach about 50%. Click "Generate New UUID" to create one, or generate up to 100 at once.

Common Use Cases for UUIDs and GUIDs

UUIDs and GUIDs are used as database primary keys, API request and correlation identifiers, distributed system node identifiers, file and resource names, message identifiers, and cache keys. They are valuable when multiple systems need to create identifiers independently. Common implementations include PostgreSQL's UUID type, .NET's Guid struct, Java's UUID class, Python's uuid module, and JavaScript's crypto.randomUUID().

Frequently Asked Questions

What is the difference between UUID and GUID?

UUID (Universally Unique Identifier) and GUID (Globally Unique Identifier) usually refer to the same 128-bit identifier format. "UUID" is the standards term used in RFC 9562, while "GUID" is the name commonly used in Microsoft ecosystems. They are designed to be globally unique, but uniqueness is probabilistic rather than guaranteed.

Is this UUID generator cryptographically secure?

Yes. This generator uses crypto.randomUUID() with a crypto.getRandomValues() fallback, providing cryptographically secure randomness for UUID generation. A random UUID alone is not a complete security design for sessions, API keys, or password-reset flows, which also require appropriate storage, expiry, rotation, and access controls.

Why use UUID v4 over other versions?

UUID v4 is useful when you want random identifiers that require no coordination and reveal no timestamp. Versions 3 and 5 are deterministic namespace-based UUIDs, while UUID v7 is time-ordered and often better for sortable database identifiers. Choose the version that matches the application's requirements.

Are my generated UUIDs private?

The UUID values are generated locally in your browser, and the generator does not submit those values to a server. The site may still load standard usage analytics as described in the privacy policy, and UUIDs should be treated as identifiers rather than secrets.