head to head · open source
fastapi vs oasdiff
fastapi has 102,471 GitHub stars, 9,913 forks, 78 open issues and last shipped 2 days ago. oasdiff has 1,371 stars, 107 forks, 50 open issues and last shipped 2 days ago. fastapi leads on adoption by 7,374% (102,471 vs 1,371 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%. fastapi 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 | ★ 102K | ★ 1.4K |
| License | MIT | Apache-2.0 |
| Written in | Python | Go |
| Last push | 2026-09-18 | 2026-09-18 |
| Forks | ⑂ 9.9K | ⑂ 107 |
| 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 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 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 oasdiff
oasdiff is a Go based, Apache 2.0 command line tool that compares OpenAPI specifications and detects breaking changes, built for API engineers and platform teams who need to know whether a spec edit will break existing API clients before it ships.
read the full oasdiff overview →
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Frequently asked questions
Is fastapi or oasdiff more popular?
fastapi has 102,471 GitHub stars and oasdiff has 1,371. 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 (102,471 stars) or its MIT licence terms. Choose oasdiff if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.