GUID Generator

Generate Globally Unique Identifiers (GUIDs) instantly

100% client-side · your data never leaves your browser
⚡
Click "Generate" to create UUIDs (v4)
💡 About UUID v4: Universally Unique Identifiers (UUIDs) are 128-bit numbers used to uniquely identify information. Version 4 UUIDs are randomly generated and have a collision probability of approximately 1 in 5.3×10³⁶.

📖 How to Use

  1. Click "Generate GUID" to create a single GUID
  2. For multiple GUIDs, enter a count (1-100) and click "Bulk Generate"
  3. Choose your preferred format from the dropdown (with/without hyphens, braces, etc.)
  4. Click "Copy" to copy a single GUID or "Copy All" for bulk generation
  5. Click "Download" to save bulk GUIDs as a text file
  6. Note: GUIDs and UUIDs are the same - this tool uses UUID v4 format

About the GUID Generator

The GUID Generator is a free, browser-based tool that creates Microsoft-compatible Globally Unique Identifiers (GUIDs) using the RFC 4122 UUID v4 standard. GUIDs are essential in .NET development, Windows programming, SQL Server databases, and COM applications. This tool generates cryptographically secure random GUIDs using your browser's crypto.randomUUID() API, ensuring true randomness and uniqueness. Whether you need a single GUID for a database record or thousands for bulk operations, this tool provides instant generation with multiple format options (standard, braces, parentheses, no-hyphens). Perfect for .NET developers, database administrators, and Windows programmers who need reliable unique identifiers. All generation happens locally in your browser - no server requests, no tracking, complete privacy.

Key Features:

  • RFC 4122 compliant GUID/UUID v4 generation with cryptographically secure randomness
  • Multiple format support: standard, with braces { }, with parentheses ( ), no hyphens, uppercase/lowercase
  • Bulk generation mode (1-10,000 GUIDs) with download capability
  • 100% client-side processing - GUIDs never leave your browser
  • Individual copy buttons and "Copy All" for bulk operations
  • Compatible with .NET Guid.Parse(), SQL Server UNIQUEIDENTIFIER, and all UUID-compatible systems

Common Use Cases:

  • SQL Server Primary Keys: Generate UNIQUEIDENTIFIER values for SQL Server tables, perfect for distributed databases and replication scenarios
  • .NET/C# Development: Create GUIDs for Entity Framework entities, ASP.NET session IDs, or any scenario requiring unique identifiers (compare with UUID Generator for cross-platform compatibility)
  • Windows COM Objects: Generate CLSIDs (Class IDs) and IIDs (Interface IDs) for COM component registration and Windows Registry entries
  • API Correlation IDs: Create request tracking IDs for distributed .NET microservices and Azure applications
  • Azure/Cloud Resources: Generate unique identifiers for Azure resources, blob storage containers, and cloud service instances

GUID Examples & .NET Implementation Patterns

C# / .NET GUID Generation

using System;

// Generate new GUID:
Guid myGuid = Guid.NewGuid();
Console.WriteLine(myGuid);
// Output: 3f2504e0-4f89-11d3-9a0c-0305e82c3301

// Different format outputs:
Console.WriteLine(myGuid.ToString());           // Standard: 3f2504e0-4f89-11d3-9a0c-0305e82c3301
Console.WriteLine(myGuid.ToString("N"));        // No hyphens: 3f2504e04f8911d39a0c0305e82c3301
Console.WriteLine(myGuid.ToString("B"));        // Braces: {3f2504e0-4f89-11d3-9a0c-0305e82c3301}
Console.WriteLine(myGuid.ToString("P"));        // Parentheses: (3f2504e0-4f89-11d3-9a0c-0305e82c3301)
Console.WriteLine(myGuid.ToString("D"));        // Default (same as ToString())

// Parse string to Guid:
Guid parsed = Guid.Parse("3f2504e0-4f89-11d3-9a0c-0305e82c3301");

Use case: Standard GUID operations in C# and .NET applications

SQL Server UNIQUEIDENTIFIER Primary Keys

-- Create table with GUID primary key:
CREATE TABLE Users (
    UserID UNIQUEIDENTIFIER PRIMARY KEY DEFAULT NEWID(),
    Email NVARCHAR(255) NOT NULL,
    Username NVARCHAR(100) NOT NULL,
    CreatedAt DATETIME DEFAULT GETDATE()
);

-- Insert with explicit GUID:
INSERT INTO Users (UserID, Email, Username)
VALUES ('3F2504E0-4F89-11D3-9A0C-0305E82C3301', '[email protected]', 'johndoe');

-- Insert with auto-generated GUID:
INSERT INTO Users (Email, Username)
VALUES ('[email protected]', 'admin');

-- Use NEWSEQUENTIALID() for better performance:
CREATE TABLE Orders (
    OrderID UNIQUEIDENTIFIER PRIMARY KEY DEFAULT NEWSEQUENTIALID(),
    UserID UNIQUEIDENTIFIER NOT NULL,
    Total DECIMAL(10,2)
);

Use case: SQL Server database design with GUID primary keys for distributed systems

Entity Framework Core with GUIDs

using Microsoft.EntityFrameworkCore;
using System;

// Entity model with GUID:
public class User
{
    public Guid Id { get; set; }
    public string Email { get; set; }
    public string Username { get; set; }
    public DateTime CreatedAt { get; set; }
}

// DbContext configuration:
public class AppDbContext : DbContext
{
    public DbSet<User> Users { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<User>()
            .Property(u => u.Id)
            .HasDefaultValueSql("NEWID()"); // SQL Server
            // .HasDefaultValueSql("gen_random_uuid()"); // PostgreSQL
    }
}

// Usage:
var user = new User
{
    Id = Guid.NewGuid(), // Or let DB auto-generate
    Email = "[email protected]",
    Username = "johndoe"
};
await context.Users.AddAsync(user);
await context.SaveChangesAsync();

Use case: Entity Framework Core models with GUID primary keys

Windows COM Object Registration

// COM Class definition with GUID attributes:
using System.Runtime.InteropServices;

[Guid("3F2504E0-4F89-11D3-9A0C-0305E82C3301")]
[ComVisible(true)]
public class MyComComponent
{
    public string GetMessage()
    {
        return "Hello from COM!";
    }
}

// Interface with GUID:
[Guid("8C7B9A5E-2F3D-4E1A-9B8C-7D6E5F4A3B2C")]
[InterfaceType(ComInterfaceType.InterfaceIsIDispatch)]
public interface IMyComInterface
{
    string GetMessage();
}

// Windows Registry entry (created during COM registration):
// HKEY_CLASSES_ROOT\CLSID\{3F2504E0-4F89-11D3-9A0C-0305E82C3301}

Use case: COM component development and Windows interop with CLSIDs/IIDs

ASP.NET Core Request Correlation

// Middleware for request tracking:
public class CorrelationIdMiddleware
{
    private readonly RequestDelegate _next;

    public async Task InvokeAsync(HttpContext context)
    {
        var correlationId = Guid.NewGuid().ToString();
        context.Items["CorrelationId"] = correlationId;
        context.Response.Headers.Add("X-Correlation-ID", correlationId);

        using (LogContext.PushProperty("CorrelationId", correlationId))
        {
            await _next(context);
        }
    }
}

// Usage in controller:
[ApiController]
[Route("api/[controller]")]
public class UsersController : ControllerBase
{
    private readonly ILogger<UsersController> _logger;

    [HttpGet]
    public IActionResult GetUsers()
    {
        var correlationId = HttpContext.Items["CorrelationId"];
        _logger.LogInformation("Fetching users - CorrelationId: {CorrelationId}", correlationId);
        // ...
    }
}

Use case: Distributed tracing in ASP.NET Core microservices

Azure Blob Storage with GUID Filenames

using Azure.Storage.Blobs;

public class FileUploadService
{
    private readonly BlobServiceClient _blobServiceClient;

    public async Task<string> UploadFileAsync(Stream fileStream, string originalFileName)
    {
        // Generate unique blob name with GUID:
        var fileGuid = Guid.NewGuid();
        var extension = Path.GetExtension(originalFileName);
        var blobName = $"{fileGuid}{extension}";

        var containerClient = _blobServiceClient.GetBlobContainerClient("uploads");
        var blobClient = containerClient.GetBlobClient(blobName);

        await blobClient.UploadAsync(fileStream);

        return blobClient.Uri.ToString();
        // Output: https://mystorageaccount.blob.core.windows.net/uploads/3f2504e0-4f89-11d3-9a0c-0305e82c3301.jpg
    }
}

// Database record:
public class UploadedFile
{
    public Guid Id { get; set; } = Guid.NewGuid();
    public string OriginalFileName { get; set; }
    public string BlobUrl { get; set; }
}

Use case: Unique file naming for Azure cloud storage to prevent conflicts

❓ Frequently Asked Questions

What is a GUID and how does it work?

A GUID (Globally Unique Identifier) is a 128-bit unique identifier used extensively in Microsoft technologies and .NET development. GUIDs are identical to UUIDs (Universally Unique Identifiers) - they use the same RFC 4122 standard and format. The term "GUID" originated from Microsoft's COM (Component Object Model) specification in the 1990s, while "UUID" is the universal industry standard term. Both represent the same 128-bit value displayed as 32 hexadecimal digits in the format: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx (8-4-4-4-12 format).

What's the difference between GUID and UUID?

There is absolutely no technical difference between GUIDs and UUIDs - they are the exact same thing with different names. "GUID" is Microsoft's terminology used in Windows, .NET, SQL Server, and COM programming, while "UUID" is the universal standard term defined in RFC 4122. Both use the same 128-bit format, same generation algorithms (typically v4 random), and same uniqueness guarantees. If you're working in .NET/C# or Windows environments, you'll typically call them GUIDs; in Java, Python, Node.js, or databases like PostgreSQL, they're called UUIDs.

Are GUIDs truly unique? What's the collision probability?

GUIDs are designed to be globally unique without coordination, with an astronomically low collision probability. With 122 random bits (in v4 GUIDs), there are 5.3×10³⁶ possible values. The probability of generating a duplicate is so low that you could generate 1 billion GUIDs per second for 85 years and still have less than a 50% chance of a single collision. For practical purposes in software development, GUIDs can be considered completely unique for database records, API identifiers, and distributed system coordination.

When should I use GUIDs vs auto-incrementing IDs?

Use GUIDs for: distributed systems where multiple servers generate records independently, public-facing identifiers (harder to enumerate/guess than sequential IDs), database replication and merging scenarios, microservices architecture, offline-first applications that sync later, and when you need globally unique identifiers without central coordination. Use auto-incrementing integers for: single-database systems, when you need guaranteed sequential ordering, when storage space is critical (4-8 bytes vs 16 bytes), or when human-readable IDs are important. Many modern applications use GUIDs for flexibility despite the storage overhead.

How do I use GUIDs in C# and .NET?

In C# and .NET, use the built-in Guid struct from the System namespace. Generate new GUIDs with Guid.NewGuid() which uses cryptographically secure random generation. Example: Guid myGuid = Guid.NewGuid(); creates a new GUID like "3f2504e0-4f89-11d3-9a0c-0305e82c3301". You can convert to string with .ToString(), compare with .Equals(), and use as database primary keys with SQL Server's UNIQUEIDENTIFIER type. Entity Framework Core supports Guid properties natively with automatic generation on insert.

What GUID formats are supported and when to use each?

GUIDs support multiple formats: (1) Standard with hyphens: 550e8400-e29b-41d4-a716-446655440000 (most common, RFC 4122 compliant); (2) Without hyphens: 550e8400e29b41d4a716446655440000 (compact, URL-safe); (3) With braces: {550e8400-e29b-41d4-a716-446655440000} (Windows Registry, COM programming); (4) With parentheses: (550e8400-e29b-41d4-a716-446655440000) (SQL Server); (5) Uppercase/lowercase variants. Use standard format for maximum compatibility, no-hyphen format for compact storage, and braces/parentheses when required by specific APIs or databases.

Can GUIDs be used as database primary keys? Performance considerations?

Yes, GUIDs work excellent as database primary keys, especially in distributed systems. Benefits include: no central coordination needed, can generate client-side before insert, safe for replication and merging, harder to enumerate. Performance considerations: GUIDs are larger (16 bytes vs 4-8 bytes for integers), which increases index size and can slow lookups slightly. Solution: Use clustered index on a separate auto-incrementing column for ordering, and use GUID as non-clustered unique index. SQL Server's NEWSEQUENTIALID() generates sequential GUIDs to improve clustering. Modern databases (PostgreSQL, MySQL 8+, SQL Server) have excellent GUID/UUID support and optimizations.

What are sequential GUIDs and when should I use them?

Sequential GUIDs (also called COMB - Combined GUID/timestamp) are GUIDs that incorporate a timestamp component, making them partially sequential while maintaining uniqueness. SQL Server's NEWSEQUENTIALID() function generates these. Benefits: Better database performance due to reduced index fragmentation, faster inserts in clustered indexes, maintains GUID uniqueness benefits. Trade-offs: Slightly more predictable than pure random GUIDs (timestamp can be inferred), may reveal record creation order. Use sequential GUIDs for high-volume database inserts where performance is critical but you still need distributed generation capabilities. Avoid for security-sensitive identifiers where unpredictability is required.

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