Check for 10 million Guids whether they are a UUID version 4. This Gist is used in my blog post https://johanvergeer.github.io/posts/net-guid-uuid-version

a-list-of-guids-version-4

              ˅
37a6ad63-700c-4404-bdd4-828575845045
b0f9f119-c667-4af7-b50c-f354e2cc235b
3553da71-f02c-49c9-8a0e-36c8d921d6ad
57fa71f7-846b-4cc1-9ccb-6849e3b473de
d83e2e66-43b6-4021-8950-7825bea500b0
95d94be0-7ea7-49a0-a19a-22d504d99ce9
68128afd-7c82-4012-8b3c-9f56a75c7628
cae534a0-cb29-4d22-a16c-70f764aedbcb
214f5a04-fbaf-4cbf-9342-ac1191ed3d27
a87969e6-7390-4164-a624-fe3327be1fa6

Program.cs

/// <summary>
/// Simple script to check whether a C# Guid is really a UUID version 4.
/// </summary>
class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine($"{"Current",-10}{"Errors found",-10}");
        Console.WriteLine($"{"-------",-10}{"------------",-10}");

        var errorsFound = 0;

        for (var i = 0; i < 10_000_000; i++)
        {
            var guid = Guid.NewGuid();
            var uuidVersion = guid.ToString().Substring(14, 1);
            var isVersion4 = uuidVersion == "4";

            if (!isVersion4)
            {
                errorsFound += 1;
            }

            Console.Write($"\r{i, -10}{errorsFound, -10}   ");
        }

        Console.WriteLine();

        Console.ReadKey();
    }
}

test-results-10-million-guids

Current   Errors found
-------   ------------
9999999   0

uuid-breakdown

                             +- UUID version
                             |
                            |-| 
 3 7 a 6 a d 6 3 - 7 0 0 c - 4 4 0 4 - b d d 4 - 8 2 8 5 7 5 8 4 5 0 4 5
|---------------| |-------| |---|---| |-------| |-----------------------|
        |             |       |   |       |                 |
        |             |       |   |       |                 +- node
        |             |       |   |       +- clock_seq_low
        |             |       |   +- clock_seq_hi_and_reserved
        |             |       +- time_hi_and_version
        |             +- time_mid
        +- time_low