Overview: Windmill is an open-source developer platform designed to transform scripts into scalable APIs, background jobs, workflows, and interactive UIs. It enables developers to build internal tools without leaving their codebase by automatically generating web interfaces from Python, TypeScript, Go, Bash, SQL, and GraphQL scripts. With its lightweight architecture and sandboxed execution environment, Windmill provides a self-hostable alternative to proprietary platforms like Retool, Pipedream, and Temporal. The platform is built for teams that need full control over their infrastructure while maintaining high performance and security, especially for internal tooling and automation at scale.
Windmill’s core value lies in its ability to bridge scripting and low-code development: write a script once, and instantly get a shareable UI, API endpoint, and workflow step. This eliminates the need to manually build forms or APIs for every small automation task. Its integration with GitHub, VS Code extension, and support for multi-language runtimes make it ideal for engineering teams looking to democratize automation without sacrificing code quality or control.
What You Get
- Auto-generated UIs from scripts - Windmill automatically generates web forms and interfaces based on script parameters, eliminating manual frontend development for internal tools. Parameters are typed and validated using TypeScript, Python type hints, or Go structs.
- Multi-language script support - Run scripts in Python, TypeScript, Go, Bash, SQL, and GraphQL with native runtime environments (Deno for TS, Bun, Python 3, Go 1.19+, etc.) and access to package managers like npm and PyPI.
- Workflow composition with flows - Chain scripts together visually using a drag-and-drop flow editor to build complex pipelines, reuse community scripts from WindmillHub, and schedule executions via cron or webhooks.
- Self-hostable with Docker/Kubernetes - Deploy Windmill on-premises or in private clouds using docker-compose, Helm charts, or standalone binaries with full control over data and infrastructure.
- Sandboxed script execution - Scripts run in isolated environments using nsjail, ensuring security for multi-tenant deployments and preventing system-level access.
- Secrets and variable management - Securely store and reference credentials, API keys, and environment variables using encrypted K/V storage per workspace with support for PostgreSQL encryption at rest.
- Webhook and cron triggers - Trigger scripts and workflows via HTTP webhooks or schedule them with cron expressions (e.g., “/5 * * * *”).
- VS Code extension for local dev - Develop and test scripts locally with real-time sync to your Windmill instance, including access to secrets and resources as if running in production.
Common Use Cases
- Building internal tooling for engineering teams - Automate CI/CD checks, database migrations, or environment audits by writing Python scripts and instantly exposing them as web UIs with form inputs and result displays.
- Creating multi-step data pipelines without Airflow - Compose Python and SQL scripts into workflows that pull data from APIs, transform it with TypeScript, then load into a warehouse—without managing complex DAGs or Docker containers.
- Problem: Manual form-building for team tools → Solution: Write a script, get a UI - Instead of building React forms to collect user input for running a database cleanup script, write the Python function in Windmill and get a fully functional web form with validation and history automatically.
- DevOps teams managing microservices across environments - Use Windmill to run health checks, log aggregators, or deploy scripts across staging and production with role-based access, secrets management, and audit trails—all self-hosted.
Under The Hood
Windmill is a low-code automation platform designed to enable developers and non-developers to build, deploy, and manage workflows using a combination of declarative schema design and multi-language script execution. The system emphasizes extensibility, cross-language support, and developer-friendly tooling to streamline workflow automation.
Architecture
Windmill follows a monolithic architecture with modularized backend, frontend, and CLI components that support cross-language execution through WASM parsers. The system is structured to separate core logic from infrastructure while enabling rich integration capabilities.
- The backend is built as a Rust monolith with distinct modules for API, database migration, and worker execution, ensuring clear separation of concerns
- The frontend is developed with Svelte and TypeScript, featuring a component-based UI architecture with strong type safety
- Cross-language support is achieved via WASM-based parsers and language-specific runtimes, enabling flexible script execution across multiple environments
- Extensive tooling is included to support deployment and development workflows, including Docker containers, CI/CD integration points, and devcontainer configurations
Tech Stack
Windmill is a multi-language system built primarily with Rust for backend services, Svelte and TypeScript for the frontend, and HTML/CSS for UI rendering. It supports a wide range of scripting languages and integrates with cloud-native infrastructure.
- The backend is powered by Rust, while the frontend leverages Svelte and TypeScript for a responsive, type-safe user interface
- The system integrates with Docker, Kubernetes, Helm, and various cloud providers to support scalable deployment and runtime environments
- Development workflows are supported through Nix for reproducible builds, multi-stage Docker builds, and CI/CD pipelines with devcontainer support
- Testing is conducted across multiple languages using a mix of unit, integration, and Svelte-specific testing utilities to ensure broad coverage
Code Quality
Windmill exhibits a mixed code quality profile with strong testing practices and consistent use of type safety, although some legacy elements indicate historical complexity.
- Comprehensive test coverage is present across backend services and frontend components, with support for multiple runtime environments
- Error handling is implemented consistently across modules, with clear patterns for logging and recovery in distributed systems
- Code style and conventions are largely maintained through linting and TypeScript usage, though some technical debt remains in older configurations
- The codebase demonstrates good adherence to modular design principles and component reuse, supporting long-term maintainability
What Makes It Unique
Windmill stands out in the automation space through its unique blend of declarative workflow design and multi-language runtime support, offering a flexible yet structured approach to low-code development.
- A multi-language parser ecosystem enables seamless integration of scripts written in various languages into a unified automation engine
- The declarative OpenFlow schema provides structured, version-controlled workflows with built-in validation and migration support
- An extensible resource model allows for custom integrations and third-party API connections through a standardized interface
- The platform features inline script editing, real-time preview, and Svelte-based UI components that deliver a responsive and component-driven developer experience