Generate Globally Unique Identifiers (GUIDs) in various Microsoft formats with our free online tool. Perfect for .NET developers, Windows applications, and COM development.
All GUIDs follow the RFC 4122 standard and are compatible with Windows applications
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How many GUIDs? (max 1000)
A GUID (Globally Unique Identifier) is Microsoft's implementation of the UUID (Universally Unique Identifier) standard. GUIDs are 128-bit values that are guaranteed to be unique across all computers worldwide and throughout time. Microsoft introduced GUIDs primarily for use in Windows development, COM (Component Object Model) programming, and the Windows Registry. While technically equivalent to UUIDs, GUIDs are often represented with specific formatting conventions and used in Microsoft-specific contexts.
While GUIDs and UUIDs refer to the same concept and follow the same technical standard (RFC 4122), there are some contextual differences in how they're used:
| Feature | GUID | UUID |
|---|---|---|
| Origin | Microsoft implementation | Open standard by IETF |
| Default Formatting | Often shown with braces: {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} | Typically shown without braces: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx |
| Common Environments | Windows, .NET, COM, Registry | Cross-platform, web applications, Unix/Linux |
| Case Convention | Traditionally uppercase in Microsoft documentation | Often lowercase in specs and documentation |
| Byte Order | First three components stored as little-endian | Canonically stored in big-endian |
| Technical Structure | 128-bits following RFC 4122 | 128-bits following RFC 4122 |
GUIDs can be represented in several formats depending on where they're used in the Microsoft ecosystem:
| Format | Example | Common Usage |
|---|---|---|
| Standard | XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX | Generic representation, cross-platform compatibility |
| Braces | {XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX} | Common in Microsoft documentation, VB, and some Windows APIs |
| Parentheses | (XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX) | Occasionally used in legacy Microsoft applications |
| Registry | HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX} | Windows Registry paths for COM objects |
| .NET Guid Attribute | [Guid("XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX")] | C# and .NET class or interface attribute |
| C# Guid Declaration | new Guid("XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX") | C# code when creating new Guid instances |
| C/C++ Structure | DEFINE_GUID(MyGuid, 0xXXXXXXXX, 0xXXXX, 0xXXXX, 0xXX, 0xXX, 0xXX, 0xXX, 0xXX, 0xXX, 0xXX, 0xXX); | C/C++ code for COM development |
GUIDs are particularly valuable in these scenarios:
GUIDs are deeply integrated into Microsoft technologies. Here are some common Microsoft-specific uses:
Technically, yes. GUIDs and UUIDs follow the same RFC 4122 standard and are structurally identical. The main differences are in terminology, representation conventions, and usage contexts. Microsoft refers to them as GUIDs, while most other platforms call them UUIDs. Microsoft implementations also tend to use braces and uppercase letters by convention.
Yes, GUIDs are commonly used as primary keys in databases, especially in distributed systems or when data might be merged from multiple sources. However, they do have larger storage requirements (16 bytes) compared to integer IDs, and can cause index fragmentation due to their random nature. SQL Server offers NEWSEQUENTIALID() to generate more index-friendly GUIDs.
Windows uses GUIDs extensively. Every COM component has a CLSID (class identifier) GUID. Device interfaces, drivers, and hardware components are identified by GUIDs. The Windows Registry stores configuration information under GUID-named keys. Active Directory objects have GUID identifiers. Even Windows Features and Updates are tracked using GUIDs.
While it's technically possible to create a GUID with a specific value, it defeats the purpose of using GUIDs, which is to guarantee uniqueness. In programming, you can construct a GUID from a specific string, but you should only do this for special cases like well-known GUIDs used as markers or for testing purposes.
Microsoft primarily implements UUID/GUID version 4 (random) by default, which provides the strongest uniqueness guarantees. Older Microsoft systems may have used version 1 (timestamp + MAC address based). Version 4 is preferred for privacy and security reasons, as version 1 could potentially expose MAC addresses.