head to head · open source
fastapi vs OpenAPI-Specification
fastapi has 104,566 GitHub stars, 10,179 forks, 78 open issues and last shipped yesterday. OpenAPI-Specification has 31,291 stars, 9,145 forks, 80 open issues and last shipped 12 days ago. fastapi leads on adoption by 234% (104,566 vs 31,291 stars). fastapi is written in Python under MIT; OpenAPI-Specification is written in Markdown under Apache-2.0. fastapi has attracted 10% as many forks as stars, OpenAPI-Specification 29%. 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 | OpenAPI-Specification | |
|---|---|---|
| GitHub stars | ★ 105K | ★ 31K |
| License | MIT | Apache-2.0 |
| Written in | Python | Markdown |
| Last push | 2026-11-02 | 2026-10-22 |
| Forks | ⑂ 10K | ⑂ 9.1K |
| 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 OpenAPI-Specification if
- You want the OpenAPI-Specification feature set and don't need the biggest community
- You prefer the Apache-2.0 license terms
- Your stack matches Markdown
- You evaluated both and OpenAPI-Specification 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 OpenAPI-Specification
The OpenAPI Specification The OpenAPI Specification is a community driven open specification within the OpenAPI Initiative, a Linux Foundation Collaborative Project. The OpenAPI Specification (OAS) defines a standard, programming language agnostic interface description for HTTP APIs. This allows both humans and computers to discover and understand the capabilities of a service without requiring access to source code, additional documentation, or inspection of network traffic. When properly defined via OpenAPI, a consumer can understand and interact with the remote service with a minimal amount of implementation…
read the full OpenAPI-Specification overview →
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Frequently asked questions
Is fastapi or OpenAPI-Specification more popular?
fastapi has 104,566 GitHub stars and OpenAPI-Specification has 31,291. fastapi has the larger community by that measure.
Are fastapi and OpenAPI-Specification free?
Both are open source. fastapi is licensed under MIT and OpenAPI-Specification under Apache-2.0. Neither carries a licence fee.
What is the difference between fastapi and OpenAPI-Specification?
fastapi is written in Python and OpenAPI-Specification in Markdown. 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 OpenAPI-Specification?
Choose fastapi if you want the larger community (104,566 stars) or its MIT licence terms. Choose OpenAPI-Specification if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.