UUIDs Made Simple: What They Are, When to Use Them, and How to Generate

What is a UUID?

A UUID is a 128‑bit value designed to be unique without a central authority. They are ideal for database keys, API request IDs, file names, and distributed systems.

Which version should I use?

• v1: time‑based with node info; predictable order but may leak host details.
• v4: random‑based; simple and widely used, collisions are astronomically unlikely.
• v7: time‑ordered with randomness; great for databases and logs needing sort‑friendly IDs.

Under the hood, v1 combines a timestamp with node information to produce sortable identifiers; v4 relies on cryptographically secure randomness for high‑entropy, non‑predictable IDs; and v7 encodes a timestamp with random bits so IDs sort naturally by time while staying hard to guess. Choose the version that best matches your privacy and ordering needs.

When are UUIDs a good fit?

• Generating IDs on the client without a round trip.
• Distributed systems where multiple writers need unique IDs.
• Identifiers that should not reveal sequence or count (use v4).
• Log/event streams that benefit from chronological ordering (use v7).

You’ll find UUIDs everywhere: database primary keys, public API resource IDs, object names in cloud storage, mobile app offline data, message queues, and audit/event trails. They avoid collisions across services and environments without central coordination, which makes them ideal for modern, distributed architectures.

How to generate UUIDs safely

1. Use a reputable library or platform API; avoid custom RNGs.
2. Pick the version based on ordering needs and privacy.
3. Validate format when consuming external inputs.
4. Avoid custom transforms unless necessary.

Try our UUID Generator to create v1, v4, and v7 values - single or bulk - entirely in your browser.

Common mistakes

• Using weak randomness sources for v4.
• Storing UUIDs as strings when your database supports binary.
• Assuming v1 is private; it exposes timing and node info.
• Sorting random v4 UUIDs and expecting meaningful order.

Best practices

• Prefer v7 for write‑heavy tables that benefit from time ordering.
• Use v4 for privacy‑friendly IDs that don’t leak timing or host info.
• Document your chosen version and why.
• Consider binary storage and proper indexing for performance.

FAQs