GUID stands for Globally Unique Identifier. UUID stands for Universally Unique Identifier. They are the same thing. Both refer to a 128-bit identifier, typically written as 32 hexadecimal digits in five groups separated by hyphens. The difference is terminology: UUID comes from the open-standards world (RFC 4122) and GUID is Microsoft's name for the same concept.
The Format
A GUID or UUID looks like this: 550e8400-e29b-41d4-a716-446655440000. It has the pattern 8-4-4-4-12 hexadecimal characters. Uppercase or lowercase hex is both valid. Some contexts (like COM objects in Windows registry) wrap the GUID in curly braces: {550e8400-e29b-41d4-a716-446655440000}.
Why Microsoft Uses "GUID"
Microsoft adopted the GUID terminology when they designed COM (Component Object Model) and ActiveX in the 1990s. Every COM interface, class, and type library is identified by a GUID. The Windows registry contains millions of GUIDs. Microsoft's .NET framework, Dynamics 365, Azure, and SQL Server all use GUID as the standard term, though the underlying format and generation are identical to UUID.
When to Use GUIDs
SQL Server has a dedicated uniqueidentifier data type for GUIDs. Azure services commonly expose resource identifiers as GUIDs. Power Platform (Dataverse, Power Automate, Power Apps) uses GUIDs as primary keys for every record in every table.
When working with any Microsoft technology stack, you will encounter the GUID terminology. The DevHexLab GUID Generator produces identifiers in exactly the format these systems expect.
GUID as a Database Primary Key
Using GUIDs as database primary keys has both advantages and trade-offs. The main advantage is that you can generate the identifier before inserting the record, which enables offline-first applications and simplifies distributed data synchronisation. The main trade-off is that random GUIDs cause random insertion order in clustered indexes, which can degrade write performance in large SQL Server tables. SQL Server's NEWSEQUENTIALID function and UUID v7 address this by generating time-ordered values.
Using the DevHexLab GUID Generator
Open the tool at /tools/developer/guid-generator. Choose the format (with or without hyphens, with or without curly braces) and the quantity. Click Generate. Copy the GUIDs for use in code, configuration, database seeds, or test fixtures.
Frequently Asked Questions
Can I use a GUID from one system as an ID in another?
GUIDs are globally unique, so yes. However, make sure both systems agree on the format (with or without hyphens, upper or lowercase). SQL Server stores them case-insensitively but some systems are case-sensitive.
Are sequential GUIDs better for performance?
Yes, in B-tree indexes. If your database has millions of rows and you are inserting at high throughput, sequential GUIDs (which maintain insert order) perform significantly better than fully random GUIDs.
Generate GUIDs for any Microsoft platform task instantly.