What is Windmill used for?

Windmill is an open-source developer platform that turns scripts into APIs, background jobs, workflows and auto-generated UIs, positioned against Retool, Pipedream and Temporal. It is a good fit for internal tools built from scripts, replacing Retool or Pipedream, and scheduled jobs and workflows with a UI.

Is Windmill open source?

Yes. Windmill is open source under a custom licence. Its source code is on GitHub at windmill-labs/windmill and is written mainly in Rust.

Yes. Windmill is open source, so the software itself is free to use under the terms of its own licence. A managed cloud version is also available, with paid plans from $10 per seat per month.

Can I self-host Windmill?

Yes. Windmill can be self-hosted on your own server or infrastructure.

What is Windmill an alternative to?

Windmill is an open-source alternative to Retool, Superblocks, Tray.ai and Microsoft Power Automate. Other open-source alternatives to Retool include Openblocks and Appsmith.

Is Windmill actively maintained?

Yes. The most recent commit to Windmill was on 2 October 2026, and the latest release is v1.821.0, published on 1 October 2026. The project has 18k stars on GitHub.

Windmill: open-source alternative to Retool, Superblocks

About Windmill

Windmill is an open-source platform for developers to run internal code as APIs, background jobs, workflows and user interfaces. It is pitched as a self-hostable alternative to Retool, Pipedream and Superblocks and as a simplified version of Temporal, and it automatically generates UIs so a script can be shared and triggered as an internal app.

Scripts can be written in languages including Python, TypeScript, Go, Bash, SQL, PowerShell, Rust and GraphQL. They can be composed into flows or used within richer apps built with its low-code builder. The backend is written in Rust on PostgreSQL, and the README describes it as a very fast self-hosted workflow engine, citing a comparison with Airflow. Sections of its documentation cover main concepts, local development, architecture, security, performance and self-hosting with Docker Compose.

Windmill is open source under AGPLv3, and Windmill Labs sells dedicated instances, commercial support and licenses, so the repository license is listed as 'Other' on GitHub. It suits engineering teams that want to turn existing scripts into reliable internal tools and automations without building each interface by hand.

Key features

Scripts turned into APIs and auto-generated UIs
Multi-language support including Python and TypeScript
Workflows composed from scripts
Low-code builder for internal apps
Rust workflow engine on PostgreSQL
Self-hosting with Docker Compose

Good fit for

→Internal tools built from scripts
→Replacing Retool or Pipedream
→Scheduled jobs and workflows with a UI

Built with: Rust; Python; TypeScript; PostgreSQL
Tags: workflow-automation; internal-tools; low-code; scripts; retool-alternative; rust; self-hosted; temporal-alternative

Windmill: questions and answers

What is Windmill used for?: Windmill is an open-source developer platform that turns scripts into APIs, background jobs, workflows and auto-generated UIs, positioned against Retool, Pipedream and Temporal. It is a good fit for internal tools built from scripts, replacing Retool or Pipedream, and scheduled jobs and workflows with a UI.
Is Windmill open source?: Yes. Windmill is open source under a custom licence. Its source code is on GitHub at windmill-labs/windmill and is written mainly in Rust.
Is Windmill free?: Yes. Windmill is open source, so the software itself is free to use under the terms of its own licence. A managed cloud version is also available, with paid plans from $10 per seat per month.
Can I self-host Windmill?: Yes. Windmill can be self-hosted on your own server or infrastructure.
What is Windmill an alternative to?: Windmill is an open-source alternative to Retool, Superblocks, Tray.ai and Microsoft Power Automate. Other open-source alternatives to Retool include Openblocks and Appsmith.
Is Windmill actively maintained?: Yes. The most recent commit to Windmill was on 2 October 2026, and the latest release is v1.821.0, published on 1 October 2026. The project has 18k stars on GitHub.