UUID Generator

What Is a UUID?

A UUID (Universally Unique Identifier), also known as GUID (Globally Unique Identifier), is a 128-bit label used to uniquely identify objects in computer systems. The standard format is 32 hexadecimal digits displayed in five groups separated by hyphens: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.

UUID v4 — Random

UUID version 4 uses cryptographically random values for all bits except two marker bits (version=4 and variant=RFC 4122). The probability of generating two identical v4 UUIDs is astronomically low — approximately 1 in 5.3 × 10³⁶. This makes them safe to generate independently without coordination.

This tool uses crypto.randomUUID() (where available) or falls back to crypto.getRandomValues(), both of which use the browser's cryptographically secure pseudo-random number generator (CSPRNG).

Common Use Cases

• Database primary keys — UUIDs avoid the coordination problem of sequential IDs across distributed systems or replicas.
• File names — Unique filenames for uploaded files prevent collisions and enumeration attacks.
• Session tokens — Random v4 UUIDs as session IDs are hard to guess (though purpose-built token generators may be preferred).
• Idempotency keys — APIs like Stripe use a UUID as an idempotency key to safely retry requests.
• Correlation IDs — Tracing requests across microservices.

Nil UUID

The nil UUID (00000000-0000-0000-0000-000000000000) is a special UUID where all 128 bits are zero. It's used as a sentinel value meaning "no UUID assigned" — similar to a null pointer. It is defined in RFC 4122 and is useful as a default/unset indicator in databases and APIs.