C# UUID Generator

Generating UUIDs in C#

• .NET calls a UUID a GUID, and Guid.NewGuid() produces a version 4 value. The Guid struct is immutable and value-typed, so it costs no allocation in a model; ToString() takes format specifiers — D for the hyphenated default, N for 32 characters with no hyphens, B for braces and P for parentheses.
• .NET 9 added Guid.CreateVersion7(), which stamps a Unix millisecond timestamp in the leading 48 bits and fills the rest with random data. That is the one to reach for on a high-insert table: sequential values keep inserts at the right edge of the index instead of scattering them, and the overload taking a DateTimeOffset lets you control the timestamp explicitly.

How to generate

1. Press Generate UUID above to mint a value in this browser — nothing is sent anywhere.
2. Copy one value with Copy, or set How many and use Copy all for a fixture list.
3. Switch Version if your code needs v7 instead of the v4 default, and turn on Formatting to match your stack's conventions.

Use Cases

• Entity Framework Core keys — a Guid Id initialised client-side, so the entity has its ID before SaveChanges.
• ASP.NET Core trace IDs — pair one per request with Activity.Current.
• SQL Server uniqueidentifier — generate in code, or use NEWSEQUENTIALID() when the insert is server-side.

How C# UUID Generator Compares

Code Examples

using System;

Guid v4 = Guid.NewGuid();           // UUID v4, random
Guid v7 = Guid.CreateVersion7();    // UUID v7, time-ordered

Console.WriteLine(v4);              // 9f2c7b41-0d3e-4a55-b6c1-8e7d9f0a1b2c
Console.WriteLine(v4.ToString("N")); // no hyphens
Console.WriteLine(v4.ToString("B")); // {with braces}
Console.WriteLine(v7);              // 0198c2f1-6d8a-72e3-b9c7-0036c639cad4

if (Guid.TryParse(input, out Guid parsed))
{
    // parsed is a valid GUID
}
else
{
    // reject — never let Guid.Parse throw on user input
}

Frequently Asked Questions

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