Comparison page

GUID vs UUID – What’s the Difference?

Understand the difference between GUID and UUID and when to use each in your applications.

GUID and UUID are often treated as the same thing because in real software they usually point to the same 128-bit identifier format.

The practical difference is mostly ecosystem and vocabulary. GUID is the term Microsoft popularized in .NET and Windows tooling, while UUID is the standards-based term used in RFC 4122 and in cross-platform libraries.

Quick comparison

GUID and UUID side by side

Feature	UUID	GUID
Definition	Universally Unique Identifier	Globally Unique Identifier
Standard	RFC 4122 term	Microsoft naming and implementation
Format	128-bit identifier	Same 128-bit identifier
Usage	Cross-platform applications and APIs	.NET and Windows ecosystem
Example	uuid.uuid4()	Guid.NewGuid()

Differences

Key differences

GUID is essentially the Microsoft name for UUID.
In most everyday development, they represent the same 128-bit identifier format.
The choice between the words usually depends on whether your context is .NET-specific or cross-platform.

Use cases

When to use each version

Use UUID when:

You are working across Python, JavaScript, Go, Java, PHP, or mixed-language systems.
Your docs, APIs, and libraries follow the RFC-style UUID terminology.
You want wording that feels standard outside the Microsoft ecosystem.

Use GUID when:

You are working in C# or .NET and the surrounding code already says Guid.
You use Microsoft tools, SQL Server, ASP.NET Core, or Windows-oriented documentation.
Your examples and code rely on Guid.NewGuid() and the .NET type system.

Tech details

Technical details that matter

Same size

Both UUID and GUID refer to a 128-bit identifier.

Same format

In practice, the textual format is usually the same dashed 36-character string.

Different naming

GUID became common in Microsoft tooling, while UUID remained the broader standards term.

Standards context

When people say UUID, they are usually referring to the IETF/RFC convention rather than a different data type.

Code examples

Language-specific snippets

UUID

Python

import uuid
uuid.uuid4()

GUID

Guid.NewGuid();

Generator

Interactive identifier tool

Both buttons below generate the same kind of random 128-bit value. The difference here is naming and developer context, not a different identifier engine.

Amount

UUID v3 and v5 are deterministic. The same namespace and name always return the same value, so bulk output is limited to one result.

Uppercase Remove dashes

Namespace Name

Generated output

Internal links

UUID v4 UUID v4 Python UUID v4 vs UUID v7 GUID Generator

FAQ

Helpful answers for developers

Is GUID the same as UUID?

In most real applications, yes. GUID is usually the Microsoft name for the same 128-bit identifier format that is more broadly called UUID.

Which should I use?

Use UUID in cross-platform docs, APIs, and libraries. Use GUID when you are working in .NET and want wording that matches C# types and Microsoft documentation.

Is GUID unique?

Like UUID, a GUID is designed to be globally unique in practice when generated correctly. The useful distinction is naming and ecosystem, not uniqueness behavior.

Summary

Short answer

Use UUID for general development, cross-platform libraries, and API documentation.

Use GUID when working in .NET. In practice, it is the same identifier format with Microsoft-oriented naming.