UUID Generator

What UUIDs are for

A UUID (Universally Unique Identifier) is a 128-bit value designed to be unique across space and time without a central coordinator. Version 4 UUIDs — the most common kind — are generated entirely from random bits. With 122 bits of entropy, the chance of collision is negligible: you could generate one billion UUIDs per second for 85 years and still have only a 50% chance of a single duplicate.

When to use UUID v4

• Database primary keys when you need to generate IDs client-side before insertion.
• Correlation IDs for tracing a request across distributed systems.
• Idempotency tokens — send the same UUID on retries to prevent duplicate writes.
• File names for uploads where you want to avoid any chance of collision.
• Session tokens, though for security-critical tokens consider longer opaque random strings.

UUID v4 vs v7

Version 7 UUIDs embed a timestamp in the leading bits, which makes them sort chronologically and improves database index locality. If your database benefits from ordered inserts (most do), v7 is usually the better modern choice. V4 remains useful when you want zero metadata leakage or need broad library compatibility.

Randomness quality

This tool uses the browser's crypto.randomUUID() which in turn uses the operating system's cryptographic random source. That is the same primitive used for generating cryptographic keys and session tokens — it is strong enough for security-critical identifiers.