TiktokenSharp 1.2.1

TiktokenSharp

This library is a C# implementation of the token count calculation, referencing OpenAI's official Rust language version. Currently, the encoding algorithms for o200k_base, cl100k_base, and p50k_base have been implemented. You can directly obtain the corresponding encoding algorithm using the model name.

Getting Started

TiktokenSharp is available as NuGet package.

using TiktokenSharp;

//use model name
TikToken tikToken = TikToken.EncodingForModel("gpt-3.5-turbo");
var i = tikToken.Encode("hello world"); //[15339, 1917]
var d = tikToken.Decode(i); //hello world

//use encoding name
TikToken tikToken = TikToken.GetEncoding("cl100k_base");
var i = tikToken.Encode("hello world"); //[15339, 1917]
var d = tikToken.Decode(i); //hello world

When using a new encoder for the first time, the required tiktoken files for the encoder will be downloaded from the internet. This may take some time. Once the download is successful, subsequent uses will not require downloading again. You can set TikToken.PBEFileDirectory before using the encoder to modify the storage path of the downloaded tiktoken files, or you can pre-download the files to avoid network issues causing download failures.

Why are the tiktoken files not integrated into the package? On one hand, this would make the package size larger. On the other hand, I want to stay as consistent as possible with OpenAI's official Python code.

If you are deploying cloud functions, such as "Azure App Service," which cannot read/write local files, please package tiktoken files(PBE Dir) with the publish files.

Below are the file download links: p50k_base.tiktoken cl100k_base.tiktoken o200k_base.tiktoken

Benchmark Test

• TiktokenSharp Version: 1.2.0
• SharpToken Version: 2.0.1
• Benchmark Project: TiktokenSharp.Benchmark

Run benchmark:

dotnet run --project TiktokenSharp.Benchmark/TiktokenSharp.Benchmark.csproj --framework net10.0 -c Release

List benchmarks:

dotnet run --project TiktokenSharp.Benchmark/TiktokenSharp.Benchmark.csproj --framework net10.0 -c Release -- --list flat

<details> <summary>Code：</summary>

private GptEncoding _sharpToken = GptEncoding.GetEncoding("cl100k_base");
private TikToken _tikToken = TikToken.GetEncoding("cl100k_base");

private string _kLongText = "King Lear, one of Shakespeare's darkest and most savage plays, tells the story of the foolish and Job-like Lear, who divides his kingdom, as he does his affections, according to vanity and whim. Lear’s failure as a father engulfs himself and his world in turmoil and tragedy.";

[Benchmark]
public int SharpToken()
{
    var sum = 0;
    for (var i = 0; i < 10000; i++)
    {
        var encoded = _sharpToken.Encode(_kLongText);
        var decoded = _sharpToken.Decode(encoded);
        sum += decoded.Length;
    }

    return sum;
}

[Benchmark]
public int TiktokenSharp()
{
    var sum = 0;
    for (var i = 0; i < 10000; i++)
    {
        var encoded = _tikToken.Encode(_kLongText);
        var decoded = _tikToken.Decode(encoded);
        sum += decoded.Length;
    }

    return sum;
}

</details>

Update

1.2.1 20260222

• Fix cache write failures in read-only environments by falling back from PBEFileDirectory/BaseDirectory to system Temp.
• Add in-memory loading fallback when both cache directories are unavailable to avoid runtime crashes.
• Upgrade TiktokenSharp.Test target framework to .NET 10.
• Move benchmark code out of TiktokenSharp.Test into dedicated project TiktokenSharp.Benchmark (net8.0 + net10.0).
• Remove --benchmark mode from test runner and keep TiktokenSharp.Test focused on functional validation.

1.2.0 20251119

• Optimize memory allocation and execution efficiency.

1.1.8 20250814

• Add Support gpt-5 models.

1.1.7 20250314

• Add Support o3 models.

1.1.6 20241224

• Optimize model name matching encoding.

1.1.5 20240913

• Add Support o1 models(o200k_base).

1.1.4 20240514

• Add Support gpt-4o(o200k_base).

1.1.0 20240408

• Optimize algorithm efficiency.

1.0.9 20240208

• Adding support for new OpenAI embeddings. by @winzig

1.0.7 20231010

• Corrected the issue where some new models could not properly obtain the encoder.

1.0.7 20231010

• Corrected the issue where some new models could not properly obtain the encoder.

1.0.6 20230625

• Replace WebClient with HttpClient, add async methods.

1.0.5 20230508

• New support for .Net Standard 2.0 has been added, making TiktokenSharp usable in the .Net Framework.

1.0.4 20230424

• Add method TikToken.GetEncoding(encodingName).

1.0.3 20230321

• GetEncodingSetting now supports the model of gpt-4 and also allows for encoding names to be directly passed in.

1.0.2 20230317

• add method TikToken.PBEFileDirectory to allow for custom storage directory of bpe files. the path needs to be set before TikToken.EncodingForModel().

1.0.1 20230313

• p50k_base encoding algorithm that supports the text-davinci-003 model.