cdp-kernel

A Jupyter kernel for TypeScript and JavaScript, extracted from the one built into Deno 2.9.6 (deno jupyter), that runs notebooks on several JavaScript runtimes. The kernel host runs on Node or Deno; the code you type runs in a separate target runtime: Node or Deno over the Chrome DevTools Protocol, or Bun, workerd and celld, which evaluate cells in-process. In principle, anything else whose inspector speaks CDP works too. The kernel can also run inside a web page, with cells in a Web Worker and no server (The browser).

Website: https://cdp-kernel.org/ · Docs: cdp-kernel.org/docs

Binder opens JupyterLab with every runtime and the example notebooks, nothing installed. A Codespace does the same in VS Code, with the repository checked out (Install › In a container).

This is early software. It passes a conformance suite derived from Deno's own Jupyter integration tests on every target, and it's packaged for npm and JSR as @tlockney/cdp-kernel, but it hasn't seen much real use yet. The support policy says which runtime versions and frontends are supported, and what may change before 1.0.

Features

• The Deno.jupyter display API (jupyter.display, md, html, svg, image, …) on every target.
• TypeScript, TSX, top-level await, and npm:/jsr: imports, with an optional lockfile.
• Deno projects (deno.json import maps, JSX settings) and Workers projects (wrangler bindings in env).
• JupyterLab's visual debugger on Node and Deno targets.
• anywidget-style widgets and Jupyter comms.
• prompt() and confirm(), interrupt that keeps state, Shift-Tab inspection, completion and history.

Install

Node 22.18+ host, from npm:

npm install -g @tlockney/cdp-kernel
cdp-kernel install --runtime node   # or deno, bun, workerd, celld

Deno host, from JSR:

deno run -A jsr:@tlockney/cdp-kernel/cli install --runtime deno

Each install writes a Jupyter kernelspec (cdp-node, cdp-deno, …). Pick it in JupyterLab or VS Code. To run notebooks with no Python installed, serve JupyterLab with Ganymede. Linux and macOS are supported; Windows isn't yet. See Install for --deno-compat, release-day installs on Deno, target runtime requirements, and installing from a checkout.

JupyterLab with every runtime and the examples, in a container:

docker run --rm -p 8888:8888 ghcr.io/tlockney/cdp-kernel

Quick start

import { format } from "npm:date-fns@4";

const now: Date = new Date();
await jupyter.display(jupyter.md`**Today** is ${format(now, "PPPP")}`);

Documentation

New to Jupyter? Start with Getting started.

• Guides: Writing notebooks, The jupyter namespace, Choosing a runtime, Widgets and comms, Debugger
• Reference: jupyter reference, Widgets and comms reference, Editor types, Known gaps, Support policy
• Internals: Architecture, Runtime integrations
• Contributing: CONTRIBUTING.md, Development, Security policy

The feasibility study behind the project covers the design, the alternatives considered (workerd, Bun, rusty_v8, FFI), and the evidence.

License

MIT. Parts are ports of Deno's Jupyter kernel, Copyright 2018-2026 the Deno authors. The debugger's MurmurHash2 follows JupyterLab's (BSD-3-Clause) and Gary Court's (MIT); their notices are in THIRD-PARTY-NOTICES. See Architecture › Provenance.