head to head · open source
fastapi vs greenmail
fastapi has 104,566 GitHub stars, 10,179 forks, 78 open issues and last shipped yesterday. greenmail has 749 stars, 205 forks, 67 open issues and last shipped yesterday. fastapi leads on adoption by 13,861% (104,566 vs 749 stars). fastapi is written in Python under MIT; greenmail is written in Java under Apache-2.0. fastapi has attracted 10% as many forks as stars, greenmail 27%. fastapi was the more recently maintained of the two, and both are self-hostable with no licence fee.
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 | greenmail | |
|---|---|---|
| GitHub stars | ★ 105K | ★ 749 |
| License | MIT | Apache-2.0 |
| Written in | Python | Java |
| Last push | 2026-11-02 | 2026-11-02 |
| Forks | ⑂ 10K | ⑂ 205 |
| 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 greenmail if
- You want the greenmail feature set and don't need the biggest community
- You prefer the Apache-2.0 license terms
- Your stack matches Java
- You evaluated both and greenmail 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 greenmail
GreenMail [ ][docker hub] [GreenMail][greenmail project site] allows developers to test email based applications, services or systems without access to a live mail server. Developers can send, receive, and verify emails by embedding GreenMail in a unit test or running it as a standalone container. GreenMail acts as a virtual (mocking/sandbox) mail server and supports common mail protocols SMTP, IMAP and POP3. [Examples][greenmail examples] [Javadoc][greenmail javadoc] [FAQ][greenmail faq] [Download][greenmail download] [Maven coordinates][maven repository com]: com.icegreen:greenmail:\ The separate GreenMail…
read the full greenmail overview →
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Frequently asked questions
Is fastapi or greenmail more popular?
fastapi has 104,566 GitHub stars and greenmail has 749. fastapi has the larger community by that measure.
Are fastapi and greenmail free?
Both are open source. fastapi is licensed under MIT and greenmail under Apache-2.0. Neither carries a licence fee.
What is the difference between fastapi and greenmail?
fastapi is written in Python and greenmail in Java. 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 greenmail?
Choose fastapi if you want the larger community (104,566 stars) or its MIT licence terms. Choose greenmail if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.