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Windmill: The Open-Source Developer Platform for Internal Tools, Workflows, and Automation

Windmill Banner

What Is Windmill?

Windmill is an open-source developer platform that lets you build internal tools, APIs, background jobs, and complex workflows — all from simple scripts. Think of it as a self-hosted alternative to Retool, Pipedream, and Superblocks, but with a unique twist: your scripts automatically become shareable UIs, and you can chain them together into powerful automation flows.

With support for Python, TypeScript, Go, Bash, SQL, GraphQL, and even Rust, Windmill meets developers where they are. You write a script with typed parameters — Windmill parses those types and generates a frontend form automatically. No more wasting time building UIs for every internal tool.

Key Features

  • Auto-generated UIs: Write a function with typed parameters and Windmill instantly creates a web form to run it
  • Flow Builder: Visually chain scripts together into multi-step workflows with branching, error handling, and scheduling
  • App Builder: Build rich, custom low-code interfaces on top of your scripts and flows
  • Multi-language: Python, TypeScript, Go, Bash, SQL, GraphQL, PowerShell, Rust, C#, Java, and more
  • Scheduling and Triggers: Cron jobs, webhooks, HTTP routes, Kafka, WebSockets, and email triggers
  • Secrets and Permissions: Built-in secrets management, workspace-level permissions, and OAuth/SSO
Windmill Code Editor

Why Self-Host Windmill?

Self-hosting Windmill gives you complete control over your internal tooling infrastructure. Your code, your secrets, your data — all running on your own infrastructure. Windmill is AGPLv3 licensed and runs entirely on Docker, making deployment straightforward. It uses Postgres as its database and leverages nsjail for secure script sandboxing.

The performance is remarkable: Windmill is benchmarked as the fastest self-hostable workflow engine, with sub-100ms job startup times for typical lightweight tasks. For teams tired of per-seat SaaS pricing for internal tools, Windmill is a liberating alternative.

Windmill Flow Builder

Conclusion

Windmill is a genuinely impressive platform that fills a real gap: making internal tool development fast, developer-friendly, and self-hosted. With 17k+ GitHub stars and an active community, it is already battle-tested at scale. If you need to build internal tools without the overhead of separate frontend and backend codebases, Windmill is worth a serious look.