What is GUID?
GUID (Globally Unique Identifier) is Microsoft's implementation of the UUID standard, a 128-bit identifier used to uniquely identify information in computer systems. GUIDs and UUIDs are essentially the same thing with different names.
Quick Facts
| Full Name | Globally Unique Identifier |
|---|---|
| Created | 1990s by Microsoft (based on UUID standard) |
| Specification | Official Specification |
How GUID Works
GUID is the term used primarily in Microsoft technologies (Windows, .NET, COM, SQL Server), while UUID is the standard term used elsewhere. Both follow the same format: 32 hexadecimal digits displayed as 8-4-4-4-12. GUIDs are generated using algorithms that ensure uniqueness without requiring a central authority. In .NET, the Guid struct provides methods for creating and manipulating GUIDs. SQL Server has the uniqueidentifier data type for storing GUIDs.
Key Characteristics
- 128-bit identifier, same as UUID
- Format: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
- Microsoft terminology for UUID
- Used extensively in Windows and .NET
- COM components identified by GUIDs (CLSID, IID)
- SQL Server uniqueidentifier type
Common Use Cases
- COM component identification (CLSID)
- Windows Registry keys
- .NET application identifiers
- SQL Server primary keys
- Active Directory object identifiers
Example
// C# GUID examples
Guid newGuid = Guid.NewGuid();
// Output: 3f2504e0-4f89-11d3-9a0c-0305e82c3301
Guid parsedGuid = Guid.Parse("3f2504e0-4f89-11d3-9a0c-0305e82c3301");
// SQL Server
-- DECLARE @id uniqueidentifier = NEWID()
-- SELECT @id
-- Result: 6F9619FF-8B86-D011-B42D-00C04FC964FF