head to head · open source
Langflow vs mailcatcher
Langflow has 155,114 GitHub stars, 10,122 forks, 1,056 open issues and last shipped yesterday. mailcatcher has 6,780 stars, 605 forks, 43 open issues and last shipped 7 days ago. Langflow leads on adoption by 2,188% (155,114 vs 6,780 stars). Langflow is written in Python under MIT; mailcatcher is written in Ruby under MIT. Langflow has attracted 7% as many forks as stars, mailcatcher 9%. Langflow 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
| Langflow | mailcatcher | |
|---|---|---|
| GitHub stars | ★ 155K | ★ 6.8K |
| License | MIT | MIT |
| Written in | Python | Ruby |
| Last push | 2026-09-22 | 2026-09-16 |
| Forks | ⑂ 10K | ⑂ 605 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Langflow if
- You weight community size — 155K stars and counting
- You want the MIT license terms
- Your stack matches Python
- You value the larger contributor base for long-term maintenance
pick mailcatcher if
- You want the mailcatcher feature set and don't need the biggest community
- You prefer the MIT license terms
- Your stack matches Ruby
- You evaluated both and mailcatcher fits your workflow better
About Langflow
Langflow is a visual builder platform for designing, testing, and deploying AI agents and retrieval augmented generation (RAG) pipelines. It lives in the Python based generative AI ecosystem and targets developers building intelligent applications. The project provides a low code interface to assemble components—such as LLMs, vector stores, memory modules, and tools—into executable workflows, while also exposing those workflows as APIs or MCP servers for integration into external applications.
read the full Langflow overview →
About mailcatcher
MailCatcher is a Ruby SMTP server that catches every message sent to it and serves those messages through a local web interface, and it is made for developers who need to inspect the email their application sends without delivering it to real recipients.
read the full mailcatcher overview →
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Frequently asked questions
Is Langflow or mailcatcher more popular?
Langflow has 155,114 GitHub stars and mailcatcher has 6,780. Langflow has the larger community by that measure.
Are Langflow and mailcatcher free?
Both are open source. Langflow is licensed under MIT and mailcatcher under MIT. Neither carries a licence fee.
What is the difference between Langflow and mailcatcher?
Langflow is written in Python and mailcatcher in Ruby. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, Langflow or mailcatcher?
Choose Langflow if you want the larger community (155,114 stars) or its MIT licence terms. Choose mailcatcher if its feature set, stack or MIT licence fits better. Both are self-hostable.