UUID Generator Guide: What Are UUIDs and How to Use Them

Universally Unique Identifiers (UUIDs) are 128-bit labels used for unique identification in computer systems. Here's everything you need to know.

What is a UUID?

A UUID is a 128-bit number represented as 32 hexadecimal digits in the format 8-4-4-4-12 (e.g., 550e8400-e29b-41d4-a716-446655440000). The total number of possible UUIDs is approximately 3.4 x 10^38 — enough to generate billions per second for centuries without collision.

UUID Versions

• UUID v1 — Based on timestamp and MAC address. Includes time information that can be extracted.
• UUID v4 — Based on random numbers. Most common version, 122 bits of randomness, used for most applications.
• UUID v7 — Based on timestamp with random suffix. Sortable by creation time, ideal for database primary keys.

When to Use UUIDs

• Database primary keys (especially in distributed systems)
• API resource identifiers
• Session tokens
• Order and transaction IDs
• File names (to avoid collisions)

UUID v4 vs UUID v7

UUID v4 is purely random and most widely supported. UUID v7 is time-ordered, which means database indexes work more efficiently (sequential inserts instead of random). For new projects, UUID v7 is often the better choice for database primary keys.

Try our UUID Generator — supports v1, v4, and v7 with batch generation up to 100 UUIDs at once.