using System;

using System.IO;

using System.IO.Compression;

using System.Text;

​

public static class Program

{

    public static void Main()

    {

        string[] urls = new string[]

        {

            "https://stackoverflow.com/questions/71884821/is-there-any-invertible-way-in-c-to-convert-a-string-into-a-smaller-one-an#comment127033258_71884821",

            "https://github.com/dotnet/runtime/blob/2d4f2d0c8f60d5f49e39f3ddbe1824648ee2b306/src/libraries/System.Private.CoreLib/src/System/Text/Encoding.cs#L77",

            "https://sharplab.io/#v2:CYLg1APgAgTAjAWAFBQMwAJabgdmQb2XWMwygBZ0BZAQwEsA7ACgEoiTCkTvsBOJgEQAJAKYAbMQHt0Ad0kAnMcAEsA3O2IBfZJqA===",

        };

        foreach (var original in urls)

        {

            Console.WriteLine($"Original:     {original.Length} chars, {original.Substring(0, 50)}...");

            var compressed = Compress(original);

            double compression = (original.Length - compressed.Length) / (double)original.Length;

            Console.WriteLine($"Compressed:   {compressed.Length} chars, compression: {compression:0.00%}");

            var decompressed = Decompress(compressed);

            Console.WriteLine($"Decompressed: {decompressed.Length} chars");

            Console.WriteLine($"Successful:   {decompressed == original}");

            Console.WriteLine();

        }

    }

​

    static string Compress(string value)

    {

        byte[] bytes = Encoding.UTF8.GetBytes(value);

        using var input = new MemoryStream(bytes);

        using var output = new MemoryStream();

        using (var gz = new GZipStream(output, CompressionLevel.SmallestSize))

            input.CopyTo(gz);

        byte[] result = output.ToArray();

        return Encoding.Latin1.GetString(result);

    }

​

    static string Decompress(string compressedValue)

    {

        byte[] bytes = Encoding.Latin1.GetBytes(compressedValue);

        using var input = new MemoryStream(bytes);

        using var output = new MemoryStream();

        using (var gz = new GZipStream(input, CompressionMode.Decompress))

            gz.CopyTo(output);

        byte[] result = output.ToArray();

        return Encoding.UTF8.GetString(result);

    }

}

​