jupyterpack

In-browser Python and JavaScript web applications for JupyterLite

jupyterpack brings in-browser Python and JavaScript web applications to the JupyterLite ecosystem. Built as a JupyterLite extension, it allows applications to run, serve, and interact fully client-side, with no backend required.

Features

• Python Web Apps: Serve Python web applications directly in the browser using JupyterLite's in-browser Python kernel. jupyterpack currently supports:

  • Dash
  • Streamlit
  • Panel
  • Shiny for Python
  • Textual
  • Vizro
  • FastHTML

  You can also use jupyterpack to serve any Flask, Starlette or Tornado application.

• JavaScript Web Apps: Bundle and serve JavaScript web applications using in-browser bundlers.

Example of each framework can be found in the demo folder.

Installation

You can install jupyterpack using pip or conda

# Install using pip
pip install jupyterpack

# Install using conda
conda install -c conda-forge jupyterpack

Try it online!

You can try it online by clicking on this badge:

Setting up JupyterLite deployment

jupyterpack currently supports only xeus-python kernel and does not support pyodide-kernel. You can refer to the xeus-python official documentation for the base setup of JupyterLite with xeus-python kernel.

Framework-specific setup

At runtime, jupyterpack can automatically install the dependencies required by the supported frameworks. Alternatively, you can preinstall framework dependencies directly into your JupyterLite build. When dependencies are preinstalled, runtime installation can be skipped by setting disableDependencies to true in your .spk file.

Below are example environment.yml files for each supported framework.

• Dash

name: xeus-kernels
channels:
  - https://repo.prefix.dev/emscripten-forge-dev
  - https://repo.prefix.dev/conda-forge
dependencies:
  - xeus-python
  - jupyterpack
  - dash
  - werkzeug>=2.2,<3.0
  - blinker>=1.5.0,<2
  - cachetools>=4.0,<7
  - pip:
      - pyodide_http

• Streamlit

name: xeus-kernels
channels:
  - https://repo.prefix.dev/emscripten-forge-dev
  - https://repo.prefix.dev/conda-forge
dependencies:
  - xeus-python
  - jupyterpack
  - blinker>=1.5.0,<2
  - cachetools>=4.0,<7
  - protobuf
  - altair
  - pyarrow
  - pip:
      - streamlit>=1.50.0
      - pyodide_http

• Shiny

name: xeus-kernels
channels:
  - https://repo.prefix.dev/emscripten-forge-dev
  - https://repo.prefix.dev/conda-forge
dependencies:
  - xeus-python
  - jupyterpack
  - pip:
      - shiny
      - shinychat
      - pyodide_http

• Panel

name: xeus-kernels
channels:
  - https://repo.prefix.dev/emscripten-forge-dev
  - https://repo.prefix.dev/conda-forge
dependencies:
  - xeus-python
  - jupyterpack
  - panel
  - pip:
      - pyodide_http

• Texual

name: xeus-kernels
channels:
  - https://repo.prefix.dev/emscripten-forge-dev
  - https://repo.prefix.dev/conda-forge
dependencies:
  - xeus-python
  - jupyterpack
  - textual
  - textual-serve
  - pip:
      - pyodide_http

• Vizro

name: xeus-kernels
channels:
  - https://repo.prefix.dev/emscripten-forge-dev
  - https://repo.prefix.dev/conda-forge
dependencies:
  - xeus-python
  - jupyterpack
  - werkzeug>=2.2,<3.0
  - blinker>=1.5.0,<2
  - cachetools>=4.0,<7
  - vizro
  - pip:
      - pyodide_http

Usage

To use jupyterpack, you need to create a .spk file that defines your web application. Here's an example structure of a React application:

my_app/
├── app.spk
├── App.js         # Your JS code
├── package.json   # Your JS dependencies
└── index.html      # HTML entry for JS apps

the app.spk is the entry point of your React app, it should contain the following content:

{
  "name": "React Example",
  "entry": "/index.html",
  "framework": "react"
}

Double-clicking the spk file to open the web app as a tab of JupyterLab.

.spk — Jupyter Pack File Format

A .spk file describes how an application should be loaded, executed, and rendered in JupyterLite and JupyterLab.
It defines the entry point, framework, optional dependencies, and runtime metadata, allowing reproducible execution across environments.

The file is expressed in JSON.

Basic Structure

interface IJupyterPackFileFormat {
  entry: string;
  framework: JupyterPackFramework;
  name?: string;
  metadata?: {
    autoreload?: boolean;
  };
  rootUrl?: string;
  dependencies?: IDependencies;
  disableDependencies?: boolean;
}

• entry (required): Path to the main entry file of the application. For examples:

  • "app.py"
  • "/index.html"
  • "dashboard/index.py"

  The path is resolved relative to the .spk file location.

• framework (required): The framework used to run the application. Supported frameworks are:

  Value	Description
  react	React-based frontend application
  dash	Plotly Dash application
  streamlit	Streamlit application
  shiny	Shiny application (Python)
  panel	Panel application
  textual	Textual application
  tornado	Tornado web application
  starlette	Starlette web application

• name (optional): The name of the application. If not provided, the name will be the name of the .spk file.

• metadata (optional): Additional metadata for the application.

  • autoreload: Enables automatic reload when source files change.

• rootUrl (optional): The root URL of the web application. Default is /

• dependencies (optional): The dependencies of the web application. It will be merged with the default dependencies of the selected framework

  • mamba: Emscripten-forge packages
  • pip: PYPI packages Example:

    dependencies: {
      mamba: ['numpy, scipy'];
      pip: ['plotly'];
    }

  You only need to specify the dependencies of the application, the required dependencies of the framework will be automatically added.

• disableDependencies (optional): Disable entirely the dependency installation. This is useful when dependencies are already provided by the environment. Default is false.

Full example

{
  "name": "Sales Dashboard",
  "entry": "app.py",
  "framework": "streamlit",
  "rootUrl": "/",
  "metadata": {
    "autoreload": true
  },
  "dependencies": {
    "mamba": ["numpy", "pandas"],
    "pip": []
  },
  "disableDependencies": false
}

Framework-specific configurations

Dash application

Same as the React application, here is the structure of a Dash application:

my_app/
├── app.spk
├── server.py         # Your Dash code

the app.spk is the entry point of your Dash app, it should contain the following content:

{
  "name": "Dash Example",
  "entry": "server.py",
  "framework": "dash"
}

For Dash applications, you must define your Dash instance as a variable named app.
Do not call app.run_server() yourself — jupyterpack is responsible for starting and managing the server lifecycle.

As with React applications, double-clicking the .spk file will open the Dash app in a new JupyterLab tab.

Streamlit application

There is no special requirement for Streamlit applications, just write your code as a standard Streamlit application and do not start the server manually — jupyterpack will handle execution and serving automatically.

Opening the .spk file will launch the Streamlit app in a new JupyterLab tab.

Shiny application

jupyterpack supports both Shiny Express and Shiny Core applications.

• Shiny Express: no special requirements.
• Shiny Core: the application instance must be assigned to a variable named app.

In both cases, the server is managed by jupyterpack, and opening the .spk file will launch the app in JupyterLab.

Panel application

There is no special requirement for Panel applications, just write your code as a standard Panel application and call .servable() on the layout you want to serve.

Textual application

You must define your Textual application as a variable named app and do not call app.run() yourself — jupyterpack is responsible for starting and managing the server lifecycle.

Vizro application

There is no special requirement for Vizro applications, just write your code as a standard Vizro application and call Vizro().build(...).run() to serve your dashboard.

FastHTML application

JupyterPack only supports async handlers with FastHTML. You must convert all synchronous handlers to async, and you should not call serve() yourself — jupyterpack is responsible for starting and managing the server lifecycle.

License

jupyterpack is licensed under the BSD-3-Clause license.