Pennant

Paid Web

What Pennant is

Pennant is an open-source web computational notebook for collaborative Markdown, JavaScript, and Python work. Connected users can edit together through Yjs synchronization and see shared code outputs update in real time. A notebook can run one cell or the full notebook, with cells using a shared execution context. CodeMirror 6 supplies the editor and connects to Yjs for collaborative editing, while BlockNote handles Markdown. Caching and offline capabilities are provided through y-indexeddb. The project includes a React application and is MIT licensed. JavaScript and Python are supported; Go and Ruby are listed as upcoming languages. Pennant has no full-stack runtime or deployment options. Its multi-repository setup uses the contributing guide for component setup, and preliminary documentation is available at docs.trypennant.com. The project invites issues, feature requests, and pull requests. The Open source plan costs nothing.

Who it suits

Pennant suits people who need shared browser notebooks for Markdown and executable JavaScript or Python. It is also relevant to contributors comfortable with an MIT-licensed, multi-repository project.

What it does well

Real-time collaborative editing and outputs
Runs cells or complete notebooks
JavaScript and Python support
Caching and offline capabilities
MIT-licensed open source

What to know first

No full-stack runtime
No deployment options
Go and Ruby are only upcoming

Plans

Plan	Billed and limits	Price
Open source	MIT licensed · no price stated	Free

As trypennant.com lists them, read 12 Oct 2026. The maker's own page has the final word.

Verdict

Pennant brings collaborative editing and shared execution to a browser notebook with offline caching. Its lack of runtime and deployment features makes it a notebook project rather than a complete application hosting stack.

Facts from Pennant's own pages

Code contributions: The README invites users to submit issues, feature requests, and pull requests. · github.com, 12 Oct 2026
Code editor: The README says CodeMirror 6 provides the coding environment and integrates with Yjs for collaborative editing. · github.com, 12 Oct 2026
Collaboration: The README says Yjs enables real-time collaboration and synchronization between users. · github.com, 12 Oct 2026
Deployment options: none · trypennant.com, 22 Sept 2026
Documentation: The README links to preliminary documentation at docs.trypennant.com. · github.com, 12 Oct 2026
Execution: Users can run individual cells or a full notebook, with a shared execution context whose outputs update in real time for connected users. · github.com, 12 Oct 2026
Full-stack runtime: No · trypennant.com, 22 Sept 2026
Interface: The repository contains the React application for the Pennant Notebook project. · github.com, 12 Oct 2026
Languages: The README describes JavaScript and Python support, and lists Go and Ruby as upcoming language support. · github.com, 12 Oct 2026
License: Pennant Notebook is MIT licensed. · github.com, 12 Oct 2026
Markdown: The README lists BlockNote as the Markdown editing component. · github.com, 12 Oct 2026
Offline persistence: The README lists caching and offline capabilities through y-indexeddb. · github.com, 12 Oct 2026
Product: Pennant is an open-source computational notebook for real-time collaboration and flexible code execution in Markdown, JavaScript, and Python. · github.com, 12 Oct 2026
Real-time collaboration: Yes · trypennant.com, 22 Sept 2026
Setup: The README says the project uses a multi-repository structure and points to its contributing guide for setup across components. · github.com, 12 Oct 2026

Where Pennant stands on Freedom251

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