head to head · open source
fastapi vs oasdiff
fastapi has 104,391 GitHub stars, 10,180 forks, 78 open issues and last shipped 2 days ago. oasdiff has 1,449 stars, 113 forks, 50 open issues and last shipped yesterday. fastapi leads on adoption by 7,104% (104,391 vs 1,449 stars). fastapi is written in Python under MIT; oasdiff is written in Go under Apache-2.0. fastapi has attracted 10% as many forks as stars, oasdiff 8%. oasdiff was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 2 topic tags (openapi, openapi3), 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 | oasdiff | |
|---|---|---|
| GitHub stars | ★ 104K | ★ 1.4K |
| License | MIT | Apache-2.0 |
| Written in | Python | Go |
| Last push | 2026-11-02 | 2026-11-03 |
| Forks | ⑂ 10K | ⑂ 113 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick fastapi if
- You weight community size — 104K stars and counting
- You want the MIT license terms
- Your stack matches Python
- You value the larger contributor base for long-term maintenance
pick oasdiff if
- You want the oasdiff feature set and don't need the biggest community
- You prefer the Apache-2.0 license terms
- Your stack matches Go
- You evaluated both and oasdiff 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 oasdiff
Command line tool to compare and detect breaking changes in OpenAPI specs. Run it locally, in CI via the GitHub Action, or use the hosted PR review workflow at oasdiff.com to approve or reject each change with a CI commit status. Get started in 30 seconds No install needed — try it with Docker against two sample specs: That prints a human readable changelog of the changes that can affect API consumers, breaking and non breaking. Swap changelog for breaking to see only the changes that break existing API clients, or diff for the full machine readable diff of the API definition, including documentation only edits…
read the full oasdiff overview →
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Frequently asked questions
Is fastapi or oasdiff more popular?
fastapi has 104,391 GitHub stars and oasdiff has 1,449. fastapi has the larger community by that measure.
Are fastapi and oasdiff free?
Both are open source. fastapi is licensed under MIT and oasdiff under Apache-2.0. Neither carries a licence fee.
What is the difference between fastapi and oasdiff?
fastapi is written in Python and oasdiff in Go. 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 oasdiff?
Choose fastapi if you want the larger community (104,391 stars) or its MIT licence terms. Choose oasdiff if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.