Ever received a .vsdx file and had no way to open it? Microsoft Visio is expensive, Windows-only, and most online converters want you to upload your diagrams to some random server. There had to be a better way.

So I built one: Visio Viewer, a Chrome extension that renders Visio files directly in your browser. No cloud. No uploads. No Visio license. Everything runs locally.

What It Does

Drop a .vsdx file onto Chrome (or use the file picker), and you get a clean SVG rendering of your diagram. The viewer supports:

• Multi-page navigation — browse all pages in a Visio document
• Zoom & pan — scroll to zoom, drag to pan, fit-to-page button
• Dark mode — because of course
• URL interception — click a link to a .vsdx file and it opens in the viewer automatically
• Open from URL — paste a URL to a remote .vsdx file

How It Works

Under the hood, the extension uses libvisio-ng — a pure Python Visio parser I built — running inside Pyodide (a full CPython compiled to WebAssembly). The entire pipeline runs in a sandboxed iframe:

1. The extension intercepts .vsdx files (via drag & drop, file picker, or URL)
2. The file is passed to libvisio-ng running in Pyodide (Python in WASM)
3. libvisio-ng parses the OPC/XML structure and produces SVG output
4. The SVG is rendered in the viewer with zoom/pan controls

All processing happens locally in your browser. No data leaves your machine. It works completely offline once installed.

Installation

Version 1.2.0 is available now:

• GitHub Release: Download the .crx or load unpacked
• Chrome Web Store: Coming soon

To install from GitHub: download the release, unzip, go to chrome://extensions, enable Developer mode, and click ”Load unpacked”.

Open Source

The extension is open source under MIT/GPL. Contributions welcome.

• GitHub Repository
• libvisio-ng blog post — the parser that powers it all