Report a bug or a broken file
The fastest route is a public issue on GitHub. Describe what you did, which tool page you used, and what happened — the issue tracker is where every bug report is triaged and fixed. If a file fails to open, include the format, the file size and the software that produced it; you never need to attach the model itself.
For anything confidential, describe the situation without attaching the model. Because the tools run locally, we usually can reproduce problems from a format description alone.
Request a format or feature
The roadmap is driven by real workflows: if you regularly need a conversion that is missing — STEP to STL, FBX to OBJ, mesh repair — say so in an issue with a sentence about your pipeline. Requests with a concrete use case get built first.
Why there is no contact form
This site has no accounts, no database and no upload path, and a traditional form would need at least one of those. The GitHub repository is the project's home: issues, discussions and pull requests all live there, and everything is answered in the open where the next user with the same question can find the answer.