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Thanks for considering contributing to Prefect!

Setting up a development environment

First, you'll need to download the source code and install an editable version of the Python package:

# Clone the repository
git clone
cd prefect

# We recommend using a virtual environment
python -m venv .venv
source .venv/bin/activate

# Install the package with development dependencies
pip install -e ".[dev]"

# Setup pre-commit hooks for required formatting
pre-commit install

If you don't want to install the pre-commit hooks, you can manually install the formatting dependencies with:

pip install $(./scripts/

You'll need to run black, autoflake8, and isort before a contribution can be accepted.

After installation, you can run the test suite with pytest:

# Run all the tests
pytest tests

# Run a subset of tests
pytest tests/

Building the Prefect UI

If you intend to run a local Prefect server during development, you must first build the UI. See UI development for instructions.

Windows support is under development

Support for Prefect on Windows is a work in progress.

Right now, we're focused on your ability to develop and run flows and tasks on Windows, along with running the API server, orchestration engine, and UI.

Currently, we cannot guarantee that the tooling for developing Prefect itself in a Windows environment is fully functional.

Prefect Code of Conduct

Our Pledge

In the interest of fostering an open and welcoming environment, we as contributors and maintainers pledge to making participation in our project and our community a harassment-free experience for everyone, regardless of age, body size, disability, ethnicity, sex characteristics, gender identity and expression, level of experience, education, socio-economic status, nationality, personal appearance, race, religion, or sexual identity and orientation.

Our Standards

Examples of behavior that contributes to creating a positive environment include:

  • Using welcoming and inclusive language
  • Being respectful of differing viewpoints and experiences
  • Gracefully accepting constructive criticism
  • Focusing on what is best for the community
  • Showing empathy towards other community members

Examples of unacceptable behavior by participants include:

  • The use of sexualized language or imagery and unwelcome sexual attention or advances
  • Trolling, insulting/derogatory comments, and personal or political attacks
  • Public or private harassment
  • Publishing others' private information, such as a physical or electronic address, without explicit permission
  • Other conduct which could reasonably be considered inappropriate in a professional setting

Our Responsibilities

Project maintainers are responsible for clarifying the standards of acceptable behavior and are expected to take appropriate and fair corrective action in response to any instances of unacceptable behavior.

Project maintainers have the right and responsibility to remove, edit, or reject comments, commits, code, wiki edits, issues, and other contributions that are not aligned to this Code of Conduct, or to ban temporarily or permanently any contributor for other behaviors that they deem inappropriate, threatening, offensive, or harmful.


This Code of Conduct applies within all project spaces, and it also applies when an individual is representing the project or its community in public spaces. Examples of representing a project or community include using an official project e-mail address, posting via an official social media account, or acting as an appointed representative at an online or offline event. Representation of a project may be further defined and clarified by project maintainers.


Instances of abusive, harassing, or otherwise unacceptable behavior may be reported by contacting Chris White at All complaints will be reviewed and investigated and will result in a response that is deemed necessary and appropriate to the circumstances. The project team is obligated to maintain confidentiality with regard to the reporter of an incident. Further details of specific enforcement policies may be posted separately.

Project maintainers who do not follow or enforce the Code of Conduct in good faith may face temporary or permanent repercussions as determined by other members of the project's leadership.


This Code of Conduct is adapted from the Contributor Covenant, version 1.4, available at

For answers to common questions about this code of conduct, see

Developer tooling

The Prefect CLI provides several helpful commands to aid development.

Start all services with hot-reloading on code changes (requires UI dependencies to be installed):

prefect dev start

Start a Prefect API that reloads on code changes:

prefect dev api

Start a Prefect agent that reloads on code changes:

prefect dev agent

UI development

Developing the Prefect UI requires that npm is installed.

Start a development UI that reloads on code changes:

prefect dev ui

Build the static UI (the UI served by prefect server start):

prefect dev build-ui

Kubernetes development

Generate a manifest to deploy a development API to a local kubernetes cluster:

prefect dev kubernetes-manifest

To access the Prefect UI running in a Kubernetes cluster, use the kubectl port-forward command to forward a port on your local machine to an open port within the cluster. For example:

kubectl port-forward deployment/prefect-dev 4200:4200

This forwards port 4200 on the default internal loop IP for localhost to the Prefect server deployment.

To tell the local prefect command how to communicate with the Prefect API running in Kubernetes, set the PREFECT_API_URL environment variable:

export PREFECT_API_URL=http://localhost:4200/api

Since you previously configured port forwarding for the localhost port to the Kubernetes environment, you’ll be able to interact with the Prefect API running in Kubernetes when using local Prefect CLI commands.