Question 1

What is a GUID?

Accepted Answer

GUID (Globally Unique Identifier) is Microsoft's terminology for UUID (Universally Unique Identifier). It's a 128-bit identifier that is functionally identical to UUID v4, using the same RFC 4122 standard. The only difference is presentation: GUIDs are typically displayed in uppercase in Microsoft ecosystems (.NET, Windows, SQL Server), while UUIDs are usually lowercase.

Question 2

Is GUID the same as UUID?

Accepted Answer

Yes, GUID and UUID are the same thing. GUID is just Microsoft's branding of the UUID standard. They use the same format (8-4-4-4-12 hexadecimal digits), the same generation algorithm, and the same level of uniqueness. You can use them interchangeably - a GUID generated here will work anywhere a UUID is expected, and vice versa.

Question 3

Why are GUIDs uppercase?

Accepted Answer

While the RFC 4122 standard doesn't specify case, Microsoft conventionally displays GUIDs in uppercase in their documentation, tools, and frameworks (.NET, SQL Server, etc.). This is purely a presentation preference - GUIDs are case-insensitive, and the same GUID in uppercase and lowercase represents the same identifier.

Question 4

When should I use GUID vs UUID?

Accepted Answer

Use GUID when working in Microsoft ecosystems (.NET applications, SQL Server databases, Windows development) to match their conventions and documentation. Use UUID terminology in cross-platform contexts, web APIs, or non-Microsoft environments. Functionally, they're identical, so it's just a naming convention to match your environment.

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