GUID Generator
Generate GUIDs (Globally Unique Identifiers) instantly — the same standard as UUID v4, used across .NET, C#, SQL Server and Azure. Bulk generate, copy in one click, choose uppercase or lowercase format. Everything runs in your browser — nothing sent to any server.
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Frequently Asked Questions
What is a GUID and how is it different from a UUID?▾
GUID (Globally Unique Identifier) and UUID (Universally Unique Identifier) are the same thing — different names for the same standard (RFC 4122).
GUID is the term used by Microsoft across Windows, .NET, C#, SQL Server, and Azure. UUID is the term used in Linux, web standards, and most open-source ecosystems. The format is identical: 32 hexadecimal digits in the pattern xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx, e.g. 550e8400-e29b-41d4-a716-446655440000.
How do I generate a GUID in C#, SQL Server, and PowerShell?▾
C# / .NET: Guid.NewGuid() returns a new random GUID. For a string: Guid.NewGuid().ToString().
SQL Server: SELECT NEWID() generates a random GUID (equivalent to UUID v4). NEWSEQUENTIALID() generates sequential GUIDs optimized for clustered index performance.
PowerShell: [System.Guid]::NewGuid() or the shorthand [guid]::NewGuid().
All three generate version 4 (random) GUIDs by default.
Are GUIDs truly unique? Can two applications ever generate the same GUID?▾
In practice, yes — GUIDs are unique for all real-world purposes. A version 4 GUID has 122 bits of randomness, giving 2¹²² possible values (~5.3 × 10³⁶). The probability of two randomly generated GUIDs colliding is astronomically small — roughly 1 in 5 undecillion.
You would need to generate about 2.7 × 10¹⁸ GUIDs before having a 50% chance of a single collision. No production system will ever hit this limit.
Should I use GUIDs or auto-increment integers as primary keys in SQL Server?▾
It depends. Auto-increment integers (IDENTITY) are smaller (4–8 bytes vs 16 bytes), faster for clustered indexes, and easier to read in queries. GUIDs are better when you need to merge data from multiple databases, generate IDs on the client before inserting, or avoid exposing sequential IDs in URLs.
The main performance concern with random GUIDs (NEWID()) as clustered keys is page fragmentation — each insert goes to a random position. The solution is NEWSEQUENTIALID() in SQL Server, which generates GUIDs that sort in insertion order and eliminate fragmentation.
What is the correct format for a GUID — uppercase or lowercase, with or without braces?▾
All of these represent the same GUID:
550e8400-e29b-41d4-a716-446655440000 (standard, lowercase) 550E8400-E29B-41D4-A716-446655440000 (uppercase) {550e8400-e29b-41d4-a716-446655440000} (with braces — common in .NET and Windows Registry) 550e8400e29b41d4a716446655440000 (no hyphens)
The RFC 4122 standard uses lowercase without braces. .NET's Guid.ToString("B") adds braces. Most parsers accept all variants — but check the requirements of the API or database column you are inserting into.