JupyLens opens, renders, and edits Jupyter Notebook (.ipynb) files directly in your browser. No Jupyter server, no Python installation, no setup — just open your notebook and start reading or editing. Important: This add-on does not execute or run notebook code. It is a viewer and editor only — you can read and edit cell source text, but code cells are never executed. Key Features

Instant Rendering: Open any .ipynb file and see it rendered with formatted markdown, syntax-highlighted Python code, and all cell outputs, including images, HTML tables, and error tracebacks.
Auto-Open: Navigate to any .ipynb file URL (local or remote) and JupyLens automatically intercepts and renders it.
13 Themes: Choose from GitHub Theme, One Dark Pro, Dracula, Monokai Pro, Tokyo Night, Ayu, One Monokai, Rose Pine, Shades of Purple, Winter Is Coming, Solarized Light, Solarized Dark, and Nord. Your selection is saved across sessions.
System-Aware Defaults: Automatically selects Ayu for dark system themes and GitHub Theme for light system themes on first launch.
Inline Editing: Click the Edit button on any cell to modify its source. Tab key inserts 4 spaces. Save commits the change; Cancel discards it. Download the modified notebook as an .ipynb file.
Line Numbers: Toggle line numbers on code cells with one click. The preference is saved automatically.
Rich Output Support: Displays stream output, execution results, display_data with base64-encoded PNG/JPEG/GIF images, inline SVG, HTML content, and error tracebacks with full ANSI color rendering (including 256-color codes).
Drag and Drop: Drop a notebook file onto the viewer to open it instantly.

Privacy JupyLens processes all notebook files entirely within your browser. No data is uploaded, transmitted, or shared with any server. The add-on stores only your theme preference and line number setting using browser.storage.local. No analytics, tracking, or third-party services are used. The add-on works completely offline. Technical Details

Manifest V2 compliant
Zero external dependencies — no npm packages, no CDN scripts, no build step
Built-in markdown parser, Python syntax highlighter, and ANSI escape code parser
All JavaScript is bundled locally within the add-on package

Support Report issues or contribute at: https://github.com/sajjad-ahmed/jupylens Developed by Sajjad Ahmed Niloy.

niloy

Published Firefox add-on:

JupyLens - Jupyter Notebook Viewer & Editor