C# API

Open-source C# projects categorized as API

Top 23 C# API Projects

  1. Bitwarden

    Bitwarden infrastructure/backend (API, database, Docker, etc). (by bitwarden)

    Project mention: Useful Sites for Privacy and Security | dev.to | 2025-03-22

    Bitwarden - Open-source password manager.

  2. Stream

    Stream - Scalable APIs for Chat, Feeds, Moderation, & Video. Stream helps developers build engaging apps that scale to millions with performant and flexible Chat, Feeds, Moderation, and Video APIs and SDKs powered by a global edge network and enterprise-grade infrastructure.

    Stream logo
  3. Jackett

    API Support for your favorite torrent trackers

    Project mention: Netflix will show generative AI ads midway through streams in 2026 | news.ycombinator.com | 2025-05-15

    https://github.com/Jackett/Jackett | https://github.com/qbittorrent/search-plugins/wiki/How-to-co...

  4. GraphQL for .NET

    GraphQL for .NET

    Project mention: Dotnet Run App.cs | news.ycombinator.com | 2025-05-28

    .NET 9 will absolutely load a library that was built targeting .NET 5.

    For instance, GraphQL was built targeting both .NET 5 and .NET Standard 2.0, as you can see towards the top of the NuGet page: https://www.nuget.org/packages/GraphQL

    .NET 9 will use the .NET 5 build, not .NET Standard 2.0. (.NET Framework 4.8.x would use .NET Standard 2.0.) Because .NET 5 > .NET Standard 2.0.

    Or Automapper 14 targets only .NET 8: https://www.nuget.org/packages/AutoMapper

    It runs on .NET 9 and .NET 10.

  5. Hot Chocolate

    Welcome to the home of the Hot Chocolate GraphQL server for .NET, the Strawberry Shake GraphQL client for .NET and Nitro the awesome Monaco based GraphQL IDE.

  6. ServiceStack

    Thoughtfully architected, obscenely fast, thoroughly enjoyable web services for all

  7. tModLoader

    A mod to make and play Terraria mods. Supports Terraria 1.4 (and earlier) installations

  8. DocFX

    Static site generator for .NET API documentation.

  9. InfluxDB

    InfluxDB – Built for High-Performance Time Series Workloads. InfluxDB 3 OSS is now GA. Transform, enrich, and act on time series data directly in the database. Automate critical tasks and eliminate the need to move data externally. Download now.

    InfluxDB logo
  10. ASP.NET MVC Boilerplate

    .NET project templates with batteries included, providing the minimum amount of code required to get you going faster.

  11. Telegram.Bot

    .NET Client for Telegram Bot API

  12. kiota

    OpenAPI based HTTP Client code generator

    Project mention: My new hobby: watching AI slowly drive Microsoft employees insane | news.ycombinator.com | 2025-05-21

    Yes but the improvements are very gradual. It takes years for something to reach maturity. At least for the web stuff which is what I know of.

    Eg:

    Minimal APIs were released in 2021 but it won't be until .NET 10 that they will have validation. Amazing that validation was not a day one priority for an API. I'm not certain if even in .NET 10 Minimal APIs will have full parity of features with MVC.

    Minification of static assets didn't come until .NET 9 released in 2024. This was already commonplace in the JS world a decade earlier. It could have been a quick win so long ago for .NET web apps.

    Blazor was released in 2018. 7 years later they still haven't fixed plenty of circuit reconnection issues. They are working on it but progress is also quite slow. Supposedly with .NET 10 session state will be able to be persist etc but it remains to be seen.

    OpenAPI is also hit and miss. Spec v3.1 released in 2021 is still not supported. Supposedly it will come with .NET 10.

    Not from .NET but they have a project called Kiota for generating clients from OpenAPI specs. It's unusable because of this huge issue that makes all properties in a type nullable. It's been open since 2023. [1]

    Etc.

    [1] https://github.com/microsoft/kiota/issues/3911

  13. ApiEndpoints

    A project for supporting API Endpoints in ASP.NET Core web applications.

  14. simulator

    A ROS/ROS2 Multi-robot Simulator for Autonomous Vehicles

  15. ChatGPT

    A ChatGPT C# client for MacOS, Windows, Linux, Android, iOS and Browser. Powered by Avalonia UI framework. (by wieslawsoltes)

  16. FFImageLoading - Fast & Furious Image Loading

    Image loading, caching & transforming library for Xamarin and Windows

  17. DSharpPlus

    A .NET library for making bots using the Discord API.

  18. data-api-builder

    Data API builder provides modern REST and GraphQL endpoints to your Azure Databases and on-prem stores.

    Project mention: Directus – real-time REST and GraphQL API of any SQL database | news.ycombinator.com | 2025-02-23

    That looks really interesting, but maybe only useful for mssql? [1]

    [1] https://github.com/azure/data-api-builder/labels/known-issue

  19. Mobius: C# API for Spark

    C# and F# language binding and extensions to Apache Spark (by microsoft)

  20. Log4Net

    Apache Log4net is a versatile, feature-rich, efficient logging API and backend for .NET

    Project mention: log4net VS Serilog - a user suggested alternative | libhunt.com/r/log4net | 2025-06-09

    Redirect the obsolete to the official: https://www.libhunt.com/r/logging-log4net

  21. WebAPI Contrib

    Community Contributions for ASP.NET Web API

  22. JsonApiDotNetCore

    A framework for building JSON:API compliant REST APIs using ASP.NET and Entity Framework Core.

  23. Twilio-csharp

    Twilio C#/.NET Helper Library for .NET6+.

  24. WatsonTcp

    WatsonTcp is the easiest way to build TCP-based clients and servers in C#.

  25. Pororoca

    An API testing tool with support for HTTP/2 and HTTP/3. Alternative to Postman.

    Project mention: These 20 Awesome API Clients Will Change How You Work with APIs | dev.to | 2025-06-11

    Pororoca is a network debugging tool focused on HTTP/2 and HTTP/3 support, making it ideal for developers exploring newer web protocols.

  26. SaaSHub

    SaaSHub - Software Alternatives and Reviews. SaaSHub helps you find the best software and product alternatives

    SaaSHub logo
NOTE: The open source projects on this list are ordered by number of github stars. The number of mentions indicates repo mentiontions in the last 12 Months or since we started tracking (Dec 2020).

C# API discussion

Log in or Post with

C# API related posts

  • Extending Methods in WebForms Core

    1 project | dev.to | 1 Jul 2025
  • CodeBehind Turns Two Years Old

    2 projects | dev.to | 30 Jun 2025
  • CodeBehind 4.2 Released

    2 projects | dev.to | 29 Jun 2025
  • WebForms Core Organization on GitHub

    3 projects | dev.to | 26 Jun 2025
  • log4net VS Serilog - a user suggested alternative

    3 projects | 9 Jun 2025
  • Migrating from WebForms to WebForms Core

    2 projects | dev.to | 26 May 2025
  • Creating an FAQ Page Without JavaScript

    2 projects | dev.to | 10 May 2025
  • A note from our sponsor - SaaSHub
    www.saashub.com | 18 Jul 2025
    SaaSHub helps you find the best software and product alternatives Learn more →

Index

What are some of the best open-source API projects in C#? This list will help you:

# Project Stars
1 Bitwarden 16,844
2 Jackett 13,624
3 GraphQL for .NET 5,946
4 Hot Chocolate 5,522
5 ServiceStack 5,468
6 tModLoader 4,622
7 DocFX 4,298
8 ASP.NET MVC Boilerplate 3,457
9 Telegram.Bot 3,440
10 kiota 3,429
11 ApiEndpoints 3,182
12 simulator 2,372
13 ChatGPT 1,469
14 FFImageLoading - Fast & Furious Image Loading 1,415
15 DSharpPlus 1,297
16 data-api-builder 1,115
17 Mobius: C# API for Spark 940
18 Log4Net 898
19 WebAPI Contrib 767
20 JsonApiDotNetCore 705
21 Twilio-csharp 693
22 WatsonTcp 633
23 Pororoca 594

Sponsored
Stream - Scalable APIs for Chat, Feeds, Moderation, & Video.
Stream helps developers build engaging apps that scale to millions with performant and flexible Chat, Feeds, Moderation, and Video APIs and SDKs powered by a global edge network and enterprise-grade infrastructure.
getstream.io