UUID Generator

Generate one or multiple universally unique identifiers (UUIDs v4)

What is it and how does it work?

A UUID generator creates universally unique identifiers — 128-bit values written as 36-character strings like 550e8400-e29b-41d4-a716-446655440000. This tool generates version 4 UUIDs, which are built from cryptographically random data: with 122 random bits, the probability of two UUIDs ever colliding is so small that you can generate billions per second for centuries before a duplicate becomes likely. That is why UUIDs are the standard way to identify database rows, API resources, files, sessions and distributed events without any central coordination.

Unlike auto-incrementing IDs, UUIDs can be generated independently on any machine — a phone, a server, a browser — and merged later without conflicts, which makes them essential in offline-first apps and microservice architectures. Generation here uses the Web Crypto API and happens fully in your browser.

Common use cases

• Database keys: use UUIDs as primary keys so records created on different servers or devices never collide when synced.
• Test data: generate batches of UUIDs to populate fixtures, mock APIs or seed files during development.
• Request tracing: tag each API request or log entry with a UUID to follow it across microservices and log aggregators.

Frequently asked questions

Can two generated UUIDs ever be the same?

Theoretically yes, practically no. A v4 UUID has 122 random bits, giving 5.3×10³⁶ possible values. You would need to generate about a billion UUIDs per second for 85 years to reach a 50% chance of a single collision.

What does "version 4" mean?

The UUID spec (RFC 4122) defines several versions. Version 4 is generated from random numbers — the most common type. Other versions use timestamps and MAC addresses (v1) or name hashing (v3/v5). The version digit appears as the first character of the third group.

Are these UUIDs cryptographically secure?

They are generated with crypto.getRandomValues(), a cryptographically secure source. Still, UUIDs are identifiers, not secrets — don't use them as passwords or API keys, since they may appear in URLs and logs.

UUID vs GUID — what's the difference?

None in practice. GUID (Globally Unique Identifier) is Microsoft's name for the same 128-bit concept. Formats are interchangeable across platforms.

Developer

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