UUID vs GUID: What is the Difference?

The Short Answer

There is effectively no difference. GUID (Globally Unique Identifier) is simply Microsoft's implementation of the UUID (Universally Unique Identifier) standard.

What is a UUID?

A UUID is a 128-bit number used to uniquely identify some object or entity on the Internet. It is standardized by the Open Software Foundation (OSF) as part of the Distributed Computing Environment (DCE).

Key features of UUIDs:

• 128-bit values (16 bytes)
• Represented as 32 hexadecimal digits
• Collisions are mathematically improbable
• Can be generated without central coordination

What is a GUID?

GUID is Microsoft's term for the same 128-bit identifier. Microsoft implemented UUIDs in their Component Object Model (COM) and called them GUIDs. The format and structure are identical to UUIDs.

When to use them?

Use UUIDs/GUIDs when you need unique keys across distributed systems without a central coordination authority. They're perfect for database primary keys in microservices, session tokens, and any scenario requiring guaranteed uniqueness.