head to head · open source
fastapi vs NSwag
fastapi has 104,566 GitHub stars, 10,179 forks, 78 open issues and last shipped yesterday. NSwag has 7,369 stars, 1,363 forks, 2,057 open issues and last shipped 2 months ago. fastapi leads on adoption by 1,319% (104,566 vs 7,369 stars). fastapi is written in Python under MIT; NSwag is written in C# under MIT. fastapi has attracted 10% as many forks as stars, NSwag 18%. fastapi was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 1 topic tag (openapi), so they are genuine substitutes rather than adjacent tools.
Two open source projects, one decision. Both are free and self-hostable — the differences are community size, license terms, language stack and release pace.
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Side by side
| fastapi | NSwag | |
|---|---|---|
| GitHub stars | ★ 105K | ★ 7.4K |
| License | MIT | MIT |
| Written in | Python | C# |
| Last push | 2026-11-02 | 2026-09-07 |
| Forks | ⑂ 10K | ⑂ 1.4K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick fastapi if
- You weight community size — 105K stars and counting
- You want the MIT license terms
- Your stack matches Python
- You value the larger contributor base for long-term maintenance
pick NSwag if
- You want the NSwag feature set and don't need the biggest community
- You prefer the MIT license terms
- Your stack matches C#
- You evaluated both and NSwag fits your workflow better
About fastapi
FastAPI framework, high performance, easy to learn, fast to code, ready for production Documentation : Source Code : FastAPI is a modern, fast (high performance), web framework for building APIs with Python based on standard Python type hints. The key features are: Fast : Very high performance, on par with NodeJS and Go (thanks to Starlette and Pydantic). One of the fastest Python frameworks available. Fast to code : Increase the speed to develop features by about 200% to 300%. Fewer bugs : Reduce about 40% of human (developer) induced errors. Intuitive : Great editor support. Completion everywhere. Less time…
read the full fastapi overview →
About NSwag
NSwag: The Swagger/OpenAPI toolchain for .NET, ASP.NET Core and TypeScript NSwag NJsonSchema Apimundo Namotion.Reflection :point right: Announcing Apimundo: An API documentation system based on NSwag and NJsonSchema :point left: NSwag is a Swagger/OpenAPI 2.0 and 3.0 toolchain for .NET, .NET Core, Web API, ASP.NET Core, TypeScript (jQuery, AngularJS, Angular 2+, Aurelia, KnockoutJS and more) and other platforms, written in C . The OpenAPI/Swagger specification uses JSON and JSON Schema to describe a RESTful web API. The NSwag project provides tools to generate OpenAPI specifications from existing ASP.NET Web API…
read the full NSwag overview →
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Frequently asked questions
Is fastapi or NSwag more popular?
fastapi has 104,566 GitHub stars and NSwag has 7,369. fastapi has the larger community by that measure.
Are fastapi and NSwag free?
Both are open source. fastapi is licensed under MIT and NSwag under MIT. Neither carries a licence fee.
What is the difference between fastapi and NSwag?
fastapi is written in Python and NSwag in C#. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, fastapi or NSwag?
Choose fastapi if you want the larger community (104,566 stars) or its MIT licence terms. Choose NSwag if its feature set, stack or MIT licence fits better. Both are self-hostable.