UUID Generator

What a UUID is

A UUID (Universally Unique Identifier, also called a GUID — Globally Unique Identifier — in some ecosystems) is a 128-bit value typically written as 32 hexadecimal digits grouped into five sections, like 550e8400-e29b-41d4-a716-446655440000. Its purpose is to identify something — a database row, a session, a file, a transaction — with an identifier that's astronomically unlikely to collide with any other UUID ever generated, anywhere, without needing a central authority to coordinate and hand out unique numbers.

This tool generates version 4 UUIDs, meaning the bits (aside from a few fixed version and variant bits required by the spec) are chosen at random using the Web Crypto API's cryptographically secure random number generator. With that much randomness, the odds of two version-4 UUIDs ever colliding are low enough to be treated as effectively zero in practice.

Why use a UUID instead of a sequential number

Sequential IDs (1, 2, 3...) are simple but reveal information — a sequential order ID tells a competitor roughly how many orders you've processed, and sequential IDs are easy to guess or enumerate, which is a real security concern for anything exposed in a URL or API. UUIDs avoid both problems: they don't leak volume information, and they can't be feasibly guessed or enumerated. They also let multiple systems generate IDs independently without needing to coordinate through a shared counter, which matters a lot in distributed systems where several servers might be creating records at the same time.

Common use cases

Developers use UUIDs as primary keys in databases, especially in distributed systems where multiple services generate records independently and a shared auto-incrementing counter isn't practical. They're used as session tokens, API keys, and request IDs for tracing a single request through logs across multiple services. Software testers generate batches of UUIDs to populate test data, and developers use them as unique identifiers for files, feature flags, and tracking events where guaranteed uniqueness matters more than a human-readable format.

Tips for working with UUIDs

If you're generating UUIDs to seed test data, this tool's bulk generation mode saves time over generating them one at a time. Keep in mind that while UUIDs are a good default for uniqueness, they're less space-efficient than sequential integers as database keys and, unlike a sequential ID, don't naturally sort in creation order — if insertion order matters for your use case, look into time-ordered variants like UUIDv7, which are outside the scope of this tool's random v4 generation but worth knowing about.

UUID versions at a glance

The UUID specification defines several versions that generate identifiers differently for different purposes. Version 1 encodes a timestamp and the generating machine's network address, which makes it sortable by creation time but can leak information about when and where it was generated. Version 4, which this tool generates, is fully random and reveals nothing about its origin or creation time, making it the most widely used version for general-purpose unique identifiers today. Version 5 generates a deterministic UUID from a namespace and a name, useful when you need the same input to always produce the same UUID. For most everyday development needs — database keys, session tokens, request IDs — version 4's combination of simplicity, randomness, and no information leakage makes it the practical default.