Open-source developer platform for internal code: APIs, background jobs, workflows and UIs. Self-hostable alternative to Retool, Pipedream, Superblocks and a simplified Temporal with autogenerated UIs and custom UIs to trigger workflows and scripts as internal apps.

Scripts are turned into sharable UIs automatically, and can be composed together into flows or used into richer apps built with low-code. Supported languages: Python, TypeScript, Go, Bash, SQL, GraphQL, PowerShell, Rust, and more.

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Windmill - Developer platform for APIs, background jobs, workflows and UIs

Windmill is fully open-sourced (AGPLv3) and Windmill Labs offers dedicated instances and commercial support and licenses.

readme_video.mp4

• Windmill - Developer platform for APIs, background jobs, workflows and UIs
  • Main Concepts
  • Show me some actual script code
  • Local Development
  • Stack
  • Fastest Self-Hostable Workflow Engine
  • Security
  • Performance
  • Architecture
  • How to self-host
    • Docker compose
    • Kubernetes (Helm charts)
    • Cloud providers
    • OAuth, SSO & SMTP
    • License
    • Integrations
  • Environment Variables
  • Run a local dev setup
    • Frontend only
    • Backend + Frontend
  • Contributing
  • Contributors
  • Copyright

Main Concepts

1. Define a minimal and generic script in Python, TypeScript, Go or Bash that solves a specific task. The code can be defined in the provided Web IDE or synchronized with your own GitHub repo (e.g. through VS Code extension): provided Web IDE or synchronized with your own GitHub repo (e.g. through VS Code extension):

2. Your scripts parameters are automatically parsed and generate a frontend.

3. Make it flow! You can chain your scripts or scripts made by the community shared on WindmillHub.

4. Build complex UIs on top of your scripts and flows.

Scripts and flows can be triggered by schedules, webhooks, HTTP routes, Kafka, WebSockets, emails, and more.

Build your entire infra on top of Windmill!

Show me some actual script code

//import any dependency  from npm
import * as wmill from "windmill-client";
import * as cowsay from "cowsay@1.5.0";

// fill the type, or use the +Resource type to get a type-safe reference to a resource
type Postgresql = {
  host: string;
  port: number;
  user: string;
  dbname: string;
  sslmode: string;
  password: string;
};

export async function main(
  a: number,
  b: "my" | "enum",
  c: Postgresql,
  d = "inferred type string from default arg",
  e = { nested: "object" }
  //f: wmill.Base64
) {
  const email = process.env["WM_EMAIL"];
  // variables are permissioned and by path
  let variable = await wmill.getVariable("f/company-folder/my_secret");
  const lastTimeRun = await wmill.getState();
  // logs are printed and always inspectable
  console.log(cowsay.say({ text: "hello " + email + " " + lastTimeRun }));
  await wmill.setState(Date.now());

  // return is serialized as JSON
  return { foo: d, variable };
}

Local Development

Windmill supports multiple ways to develop locally and sync with your instance:

Tool	Description
CLI	Sync scripts from local files or GitHub, run scripts/flows from the command line
VS Code Extension	Edit and test scripts & flows directly from VS Code / Cursor with full IDE support
Git Sync	Two-way sync between Windmill and your Git repository
Claude Code	AI-assisted development with Claude for scripts, flows, and apps

landingscripts-local.mp4

You can run scripts locally by passing the right environment variables for the wmill client library to fetch resources and variables from your instance. See local development docs.

Stack

• Database: Postgres (compatible with Aurora, Cloud SQL, Neon, Azure PostgreSQL)
• Backend: Rust - stateless API servers and workers pulling jobs from a Postgres queue
• Frontend: Svelte 5
• Sandboxing: nsjail and PID namespace isolation
• Runtimes:
  • TypeScript/JavaScript: Bun (default); Deno only on the windmill-full images
  • Python: python3 with uv for dependency management
  • Go, Bash, PowerShell, PHP, Rust, C#, Java, Ansible

Fastest Self-Hostable Workflow Engine

We have compared Windmill to other self-hostable workflow engines (Airflow, Prefect & Temporal) and Windmill is the most performant solution for both benchmarks: one flow composed of 40 lightweight tasks & one flow composed of 10 long-running tasks.

All methodology & results on our Benchmarks page.

Security

• Sandboxing: nsjail for filesystem/resource isolation, and PID namespace isolation (enabled by default) to prevent jobs from accessing worker process memory
• Secrets: One encryption key per workspace for credentials stored in Windmill's K/V store. We recommend encrypting the Postgres database as well.

See Security documentation for details.

Performance

Once a job started, there is no overhead compared to running the same script on the node with its corresponding runner (Deno/Go/Python/Bash). The added latency from a job being pulled from the queue, started, and then having its result sent back to the database is ~50ms. A typical lightweight deno job will take around 100ms total.

Architecture

How to self-host

For detailed setup options, see Self-Host documentation.

Docker compose

Deploy Windmill with 3 files (docker-compose.yml, Caddyfile, .env):

curl https://raw.githubusercontent.com/windmill-labs/windmill/main/docker-compose.yml -o docker-compose.yml
curl https://raw.githubusercontent.com/windmill-labs/windmill/main/Caddyfile -o Caddyfile
curl https://raw.githubusercontent.com/windmill-labs/windmill/main/.env -o .env

docker compose up -d

Go to http://localhost - default credentials: admin@windmill.dev / changeme

Using an external database: Set DATABASE_URL in .env to point to your managed Postgres (AWS RDS, GCP Cloud SQL, Azure, Neon, etc.) and set db replicas to 0.

Kubernetes (Helm charts)

helm repo add windmill https://windmill-labs.github.io/windmill-helm-charts/
helm install windmill-chart windmill/windmill --namespace=windmill --create-namespace

See windmill-helm-charts for configuration options.

Cloud providers

Windmill works on AWS (EKS/ECS), GCP, Azure, Ubicloud, Fly.io, Render.com, Hetzner, Digital Ocean, and others. Rule of thumb: 1 worker per 1vCPU and 1-2 GB RAM.

OAuth, SSO & SMTP

Configure OAuth and SSO (Google Workspace, Microsoft/Azure, Okta) directly from the superadmin UI. See documentation.

License

The Community Edition is free to use internally. For commercial redistribution or managed services, contact sales@windmill.dev. See LICENSE and Pricing for details.

The "Community Edition" of Windmill available in the docker images hosted under ghcr.io/windmill-labs/windmill and the github binary releases contains the files under the AGPLv3 and Apache 2 sources but also includes proprietary and non-public code and features which are not open source and under the following terms: Windmill Labs, Inc. grants a right to use all the features of the "Community Edition" for free without restrictions other than the limits and quotas set in the software and a right to distribute the community edition as is but not to sell, resell, serve Windmill as a managed service, modify or wrap under any form without an explicit agreement.

The binary compilable from source code in this repository without the "enterprise" feature flag is open-source under the LICENSE-AGPLv3 License terms and conditions.

To re-expose directly any Windmill parts to your users as a feature of your product, with the exception of iframed public Windmill "apps", or to build a feature on top of "Windmill Community Edition" that you sell commercially or embed in a distributable product or binary, you must get a commercial license. Contact us at sales@windmill.dev if you have any questions. To do the same from the binary compiled from the source code in this repository without the "enterprise" feature flag, you must comply with the AGPLv3 license terms and conditions or get a commercial license from Windmill Labs, Inc.

To use Windmill "Community Edition" as is internally in your organization, or to use its APIs as is, you do NOT need a commercial license.

Integrations

In Windmill, integrations are referred to as resources and resource types. Each Resource has a Resource Type that defines the schema that the resource needs to implement.

On self-hosted instances, you might want to import all the approved resource types from WindmillHub. A setup script will prompt you to have it being synced automatically everyday.

Environment Variables

Environment Variable name	Default	Description	Api Server/Worker/All
DATABASE_URL		The Postgres database url.	All
WORKER_GROUP	default	The worker group the worker belongs to and get its configuration pulled from	Worker
MODE	standalone	The mode if the binary. Possible values: standalone, worker, server, agent	All
METRICS_ADDR	None	(ee only) The socket addr at which to expose Prometheus metrics at the /metrics path. Set to "true" to expose it on port 8001	All
JSON_FMT	false	Output the logs in json format instead of logfmt	All
BASE_URL	http://localhost:8000	The base url that is exposed publicly to access your instance. Is overriden by the instance settings if any.	Server
ZOMBIE_JOB_TIMEOUT	30	The timeout after which a job is considered to be zombie if the worker did not send pings about processing the job (every server check for zombie jobs every 30s)	Server
RESTART_ZOMBIE_JOBS	true	If true then a zombie job is restarted (in-place with the same uuid and some logs), if false the zombie job is failed	Server
NATIVE_MODE	false	Enable native mode: sets NUM_WORKERS=8, rejects non-native jobs (nativets, postgresql, mysql, etc.)	Worker
SLEEP_QUEUE	50	The number of ms to sleep in between the last check for new jobs in the DB. It is multiplied by NUM_WORKERS such that in average, for one worker instance, there is one pull every SLEEP_QUEUE ms.	Worker
KEEP_JOB_DIR	false	Keep the job directory after the job is done. Useful for debugging.	Worker
EXIT_AFTER_N_JOBS	None	Exit the worker process after it has executed that many jobs, so that a supervisor restarts it and no process runs more than that many, bar the steps of a same-worker flow it has started, which it always finishes (set it to 1 for a process per job; jobs handed to a dedicated worker, and the worker's own init and periodic scripts, do not count). Not counting the init and periodic scripts means they run again on every restart: an init script's runtime is added to the latency of every batch of that many jobs, and a periodic script fires once per process start whatever its interval says. The worker's shell in the workers page also starts backed off rather than after the two minutes it otherwise takes, since a process due to be recycled cannot count on living that long: the first command of a session can wait up to 15s, later ones are immediate. For deployments that isolate executions by process lifetime rather than with nsjail; note that a container restart resets the process, not the container filesystem, so caches and /tmp survive it. The worker name is then derived from the hostname instead of being random, so the restarted worker keeps its row in the workers list (an agent worker keeps the row but restarts its job count). Use one worker per process: workers of one process share its environment, so the first to reach the limit shuts the others down too.	Worker
WORKER_SUFFIX	None	Pins the last part of the worker name, which is otherwise random, so that a restarted worker keeps its row in the workers list. Only needed when several worker processes of the same worker group run on one host, since the name is derived from the hostname: give each of them a distinct value, as two processes sharing one must never happen. At most 64 letters, digits and underscores; anything else is refused at startup.	Worker
LICENSE_KEY (EE only)	None	License key checked at startup for the Enterprise Edition of Windmill	Worker
SLACK_SIGNING_SECRET	None	The signing secret of your Slack app. See Slack documentation	Server
COOKIE_DOMAIN	None	The domain of the cookie. If not set, the cookie will be set by the browser based on the full origin	Server
DENO_PATH	/usr/bin/deno	The path to the deno binary.	Worker
PYTHON_PATH		The path to the python binary if wanting to not have it managed by uv.	Worker
GO_PATH	/usr/bin/go	The path to the go binary.	Worker
GOPRIVATE		The GOPRIVATE env variable to use private go modules	Worker
GOPROXY		The GOPROXY env variable to use	Worker
NETRC		The netrc content to use a private go registry	Worker
PY_CONCURRENT_DOWNLOADS	20	Sets the maximum number of in-flight concurrent python downloads that windmill will perform at any given time.	Worker
PATH	None	The path environment variable, usually inherited	Worker
HOME	None	The home directory to use for Go and Bash , usually inherited	Worker
DATABASE_CONNECTIONS	50 (Server)/3 (Worker)	The max number of connections in the database connection pool	All
SUPERADMIN_SECRET	None	A token that would let the caller act as a virtual superadmin superadmin@windmill.dev	Server
TIMEOUT_WAIT_RESULT	20	The number of seconds to wait before timeout on the 'run_wait_result' endpoint	Worker
QUEUE_LIMIT_WAIT_RESULT	None	The number of max jobs in the queue before rejecting immediately the request in 'run_wait_result' endpoint. Takes precedence on the query arg. If none is specified, there are no limit.	Worker
DENO_AUTH_TOKENS	None	Custom DENO_AUTH_TOKENS to pass to worker to allow the use of private modules	Worker
DISABLE_RESPONSE_LOGS	false	Disable response logs	Server
CREATE_WORKSPACE_REQUIRE_SUPERADMIN	true	If true, only superadmins can create new workspaces	Server
MIN_FREE_DISK_SPACE_MB	15000	Minimum amount of free space on worker. Sends critical alert if worker has less free space.	Worker
RUN_UPDATE_CA_CERTIFICATE_AT_START	false	If true, runs CA certificate update command at startup before other initialization	All
RUN_UPDATE_CA_CERTIFICATE_PATH	/usr/sbin/update-ca-certificates	Path to the CA certificate update command/script to run when RUN_UPDATE_CA_CERTIFICATE_AT_START is true	All
GOOGLE_APPLICATION_CREDENTIALS	None	(ee only) Credentials file for GCP Pub/Sub triggers that authenticate as the instance rather than through a gcloud resource (workspace admins only). Application default credentials also resolve the gcloud well-known file and the GCE metadata server. Workload Identity Federation files work with the file, url and aws credential sources; the executable source is not supported.	Server

Run a local dev setup

We recommend using Nix. See ./frontend/README_DEV.md for all options.

Frontend only

Uses the backend of https://app.windmill.dev with local frontend (hot-reload):

cd frontend
npm install
npm run generate-backend-client  # or generate-backend-client-mac on Mac
npm run dev

Windmill available at http://localhost/

Backend + Frontend

See the ./frontend/README_DEV.md file for all running options.

1. Start a local Postgres database using for instance the start-dev-db.sh script which will make a database available at postgres://postgres:changeme@localhost:5432/windmill Then run the migrations using the following command:

   cargo install sqlx-cli
   env DATABASE_URL=<YOUR_DATABASE_URL> sqlx migrate run
   

   This will also avoid compile time issue with sqlx's query! macro.
2. (optional, linux only) Install nsjail and have it accessible in your PATH
3. Install bun and python3 (+ any languages you want to use), have the bins at /usr/bin/bun and /usr/local/bin/python3 or set the corresponding environment variables.
4. (optional) Install the lld linker
5. Go to frontend/:
   1. npm install, npm run generate-backend-client then REMOTE=http://localhost:8000 npm run dev
   2. You might need to set some extra heap space for the node runtime export NODE_OPTIONS="--max-old-space-size=4096"
   3. Create an empty frontend/build folder using mkdir frontend/build
6. Go to backend/:
   1. env DATABASE_URL=<YOUR_DATABASE_URL> RUST_LOG=info cargo run
   2. You can specify any feature flag you want to enable, for example cargo run --features python to enable the python executor.
7. Windmill should be available at http://localhost:3000

Contributing

At this time, we are not seeking outside contribution. Bug reports and feature requests remain very welcome, and small, trivially-verified PRs that fix a problem are still accepted. See CONTRIBUTING.md for the full policy.

Contributors

Copyright

© 2023-2026 Windmill Labs, Inc.