Thanks for contributing to JupyterLite!

We follow Project Jupyter’s Code of Conduct for a friendly and welcoming collaborative environment.


Get the Code

git clone

if you don’t have git yet, you might be able to use the instructions below to get it


You’ll need:

  • git

  • nodejs >=12

  • yarn <2

  • python >=3.8

Various package managers on different operating systems provide these.

A recommended approach for any platform is to install Mambaforge and use the Binder environment description checked into the repo.

mamba env update --file .binder/environment.yml
mamba activate jupyterlite-dev

For speed, in GitHub Actions, python and nodejs are installed directly. Provided you already have these, to install the full development stack:

python -m pip install -r requirements-docs.txt -r requirements-lint.txt

Development Tasks


doit handles the full software lifecycle, spanning JavaScript to documentation building and link checking. It understands the dependencies between different nested tasks, usually as files that change on disk.

List Tasks

To see all of the tasks available, use the list action:

doit list --all --status

To get information about a specific task, use the info info action with the task name from the first column of list:

doit info build:js:app:retro

Task and Action Defaults

The default doit action is run which… runs the named tasks.

The default tasks are lint, build and docs:app:build, so the following are equivalent:

doit lint build docs:app:build
doit run lint build docs:app:build

doit auto

On Linux and MacOS, doit auto (which can also accept task names) will watch all files and perform any dependent tasks, then reload the tasks, useful for rapidly seeing changes.

By default, auto will invoke doit lint which may change source files. This can be confusing to IDEs (or the watch:docs and watch:js tasks) that might be performing their own watching, or run up against file system limits.

Core JavaScript development

The JupyterLite core JS development workflow builds:

  • a ready-to-serve, empty website with:

    • a lab/index.html and supporting assets

    • a retro/*/index.html and supporting assets (for tree, editor, etc.)

    • common configuration tools

  • typedoc documentation

  • TBD: a set of component tarballs distributed on See #7.


  • a set of packages in the @jupyterlite namespace, , written in TypeScript

  • some buildutils

  • some webpack configuration

  • some un-compiled, vanilla JS for very early-loading utilities

    • TODO: fix this, perhaps with jsdoc tags

While most of the scripts below will be run (in the correct order based on changes) by doit, the following scripts (defined in package.json) are worth highlighting.

Quick start

Most of the development tasks can be run with one command:

yarn bootstrap

Install JavaScript Dependencies


Build Apps

To build development assets:

yarn build

To build production assets:

yarn build:prod

Serve Apps

These are not real server solutions, but they will serve all of the assets types (including .wasm) correctly for JupyterLite development, testing, and demo purposes.

To serve with scripts/serve.js, based on Node.js’s http module:

yarn serve

To serve with Python’s built-in http.server module (requires Python 3.7+):

yarn serve:py

Watch Sources

yarn watch

Lint/Format Sources

yarn lint

Run Unit Tests

yarn build:test
yarn test

Lab Extension development

TBD: describe how the @jupyterlite/labextension works with e.g. real serverextensions

(Browser) Python Development

TBD: describe successor to pyolite, patches, etc. See #151.

(Server) Python Development

After all the yarn-related work has finished, the terminal-compatible python uses the npm-compatible tarball of app to build new sites combined with original user content.

On testing

Extra PYTEST_ARGS can be passed as a (gross) JSON string:

PYTEST_ARGS='["-s", "-x", "--ff"]' doit test:py:jupyterlite

Several tasks invoke the jupyter lite CLI, which is further described in the main docs site.


The documentation site, served on, uses information from different parts of the software lifecycle (e.g. contains an archive of the built app directory), so using the doit tools are recommended.

Build Documentation

doit docs

Extra sphinx-build arguments are set by the SPHINX_ARGS environment variable. For example to fail on all warnings (the configuration for the ReadTheDocs build):

SPHINX_ARGS='["-W"]' doit docs

Watch Documentation

doit watch:docs

This also respects the SPHINX_ARGS variable. If working on the theme layer, SPHINX_ARGS='["-a", "-j8"]' is recommended, as by default static assets are not included in the calculation of what needs to be updated.

Community Tasks


JupyterLite features and bug fixes start as issues on GitHub.

  • Look through the existing issues (and pull requests!) to see if a related issue already exists or is being worked on

  • If it is new:

    • Start a new issue

    • Pick an appropriate template

    • Fill out the template

    • Wait for the community to respond

Pull Requests

JupyterLite features and fixes become real as pull requests.

Pull requests are a great place to discuss work-in-progress, but it is highly recommended to create an issue before starting work so the community can weigh in on choices.

  • Fork the repo

  • Make a new branch off main

  • Make changes

  • Run doit

  • Push to your fork

  • Start the pull request

    • your git CLI should offer you a link, as will the GitHub web UI

    • reference one or more issue so those that are interested can find your work

      • adding magic strings like fixes #123 help tie the collaboration history together

  • Wait for continuous integration

    • If stuff breaks, fix it or ask for help!


Each pull request is built and deployed on ReadTheDocs. You can view the live preview site by clicking on the ReadTheDocs check:



Additionally, several build artifacts are available from the each run on the Actions page, including:

  • test reports

  • installable artifacts

  • an app archive ready to be used as the input to the jupyter lite CLI with all the demo content and supporting extensions.

You must be logged in to GitHub to download these.


TBD: See #121.