head to head · open source
fastapi vs OpenAPI-Specification
fastapi has 102,402 GitHub stars, 9,903 forks, 78 open issues and last shipped 4 days ago. OpenAPI-Specification has 31,215 stars, 9,156 forks, 80 open issues and last shipped 7 days ago. fastapi leads on adoption by 228% (102,402 vs 31,215 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 | ★ 102K | ★ 31K |
| License | MIT | Apache-2.0 |
| Written in | Python | Markdown |
| Last push | 2026-09-14 | 2026-09-11 |
| Forks | ⑂ 9.9K | ⑂ 9.2K |
| 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 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 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 OpenAPI-Specification
The OpenAPI Specification (OAS) is a community driven open specification hosted within the OpenAPI Initiative, a Linux Foundation Collaborative Project. It defines a standard, programming language agnostic interface description for HTTP APIs, represented in YAML or JSON. The specification lives in the HTTP API tooling ecosystem, alongside the tools, libraries, and implementations listed in the repository's implementations document. The project source is released under the Apache 2.0 license, and its GitHub repository has accumulated roughly 31,000 stars and 9,100 forks across 13 years of activity.…
read the full OpenAPI-Specification overview →
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Frequently asked questions
Is fastapi or OpenAPI-Specification more popular?
fastapi has 102,402 GitHub stars and OpenAPI-Specification has 31,215. 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 (102,402 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.