UUID vs GUID: What They Are and When to Use Them

As applications scale across many servers and databases, relying on a simple auto-incrementing ID becomes a problem. UUIDs solve this by letting any system generate a globally unique identifier without coordinating with a central authority.

What Is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit value, usually written as 32 hexadecimal digits in five groups separated by hyphens. The number of possible UUIDs is so vast that the chance of two randomly generated values colliding is effectively zero.

Example UUID:
123e4567-e89b-12d3-a456-426614174000

Format: 8-4-4-4-12 hexadecimal digits

UUID vs GUID: Are They Different?

In practice, UUID and GUID (Globally Unique Identifier) refer to the same thing. GUID is simply Microsoft's term, used across Windows and .NET, while UUID is the term from the broader standard. They share the same format and are interchangeable in almost every context.

Common UUID Versions

• Version 1: based on timestamp and the machine's MAC address. Sortable by time, but leaks hardware info.
• Version 4: fully random. The most widely used version for general-purpose IDs.
• Version 7: newer, time-ordered and random, ideal as a database key because it sorts naturally by creation time.

When to Use UUIDs

• Distributed systems where multiple nodes create records independently.
• Public-facing IDs where you do not want to expose sequential counts.
• Merging data from multiple databases without key collisions.
• Client-generated IDs created before a record reaches the server.

Prefer UUID v4 for general randomness, or v7 when you want database keys that also sort by creation time.

The UUID Generator creates cryptographically random identifiers instantly in your browser, and a bulk mode is available when you need many at once.