head to head · open source
fastapi vs NSwag
fastapi has 102,402 GitHub stars, 9,903 forks, 78 open issues and last shipped 4 days ago. NSwag has 7,365 stars, 1,360 forks, 2,057 open issues and last shipped 11 days ago. fastapi leads on adoption by 1,290% (102,402 vs 7,365 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 | ★ 102K | ★ 7.4K |
| License | MIT | MIT |
| Written in | Python | C# |
| Last push | 2026-09-14 | 2026-09-07 |
| Forks | ⑂ 9.9K | ⑂ 1.4K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick fastapi if
- You weight community size — 102K 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 is an MIT licensed, high performance Python web framework for building APIs with standard Python type hints, aimed at Python developers and teams that need production ready HTTP services with automatic OpenAPI documentation.
read the full fastapi overview →
About NSwag
NSwag is an MIT licensed Swagger/OpenAPI 2.0 and 3.0 toolchain written in C for .NET, ASP.NET Core, and TypeScript developers who need to generate OpenAPI specifications from ASP.NET Web API controllers and generate C or TypeScript clients from those specifications.
read the full NSwag overview →
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Frequently asked questions
Is fastapi or NSwag more popular?
fastapi has 102,402 GitHub stars and NSwag has 7,365. 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 (102,402 stars) or its MIT licence terms. Choose NSwag if its feature set, stack or MIT licence fits better. Both are self-hostable.