Office File Viewer (docx · xlsx · pptx)

A VS Code extension that renders Microsoft Office Open XML files inside the editor — no Office install, no server-side conversion, no export step.

Rendering is powered by @silurus/ooxml, an open-source Rust/WebAssembly + Canvas 2D engine that parses and paints .docx, .xlsx and .pptx entirely locally. Files never leave your machine.

Features

• Word (.docx / .docm) — paginated layout, toolbar page navigation, zoom, fit-width and full-document find with highlight.
• PowerPoint (.pptx / .pptm) — slide navigation, zoom, fit-width, full-deck find.
• Excel (.xlsx / .xlsm) — the engine's full workbook UI: sheet tabs, frozen panes, range selection with TSV copy, zoom slider, cached formulas, number formats and charts.
• Hyperlinks inside documents open through VS Code (http, https, mailto, tel only).
• The view live-refreshes when the file changes on disk (re-run your generator, the viewer updates).
• Theme-aware UI (light/dark/high-contrast), keyboard shortcuts, works in Remote/WSR windows (files are read via the VS Code file system API).

The viewers are read-only; use Open With… → Text Editor as a fallback escape hatch.

Settings

Settings are applied when an editor is (re)opened.

Offline by default

With the default settings the extension makes no network requests while rendering:

• The WASM parsers, webview scripts and all engine code ship inside the extension and are served from its own resources; the webview Content-Security-Policy allows only the extension's local resource origin (data:/blob: workers for the sandboxed parser worker) — no internet host is permitted.
• Text is laid out with locally installed system fonts (no webfont CDN). Non-Latin text uses your system's font fallbacks.
• Optional chart engines (MathJax equations, 3-D charts, ChartEx, region maps) and the TIFF codec are deliberately not bundled; documents using them render placeholders instead of fetching renderer code.
• The only user-triggered network actions are: clicking a hyperlink inside a document (opens the browser via VS Code, http/https/mailto/tel), and enabling officeFileViewer.useGoogleFonts (then the renderer fetches fonts from fonts.googleapis.com / fonts.gstatic.com only).

How it works

• Each format is registered as a VS Code custom read-only editor (modeled on the custom-editor-sample).
• The extension host reads the file bytes (vscode.workspace.fs) and posts them to the webview; the bundled @silurus/ooxml engine parses (WASM) and renders (Canvas 2D) there.
• The parser WASM ships beside the webview bundle (out/media/assets/*.wasm) and is resolved via the webview <base>; the Content-Security-Policy only ever allows the extension's own resources (plus Google Fonts when you opt in).

Development

npm install
npm run compile      # esbuild: extension + 3 webview bundles + wasm assets
npm run typecheck    # tsc for extension (node) and webview (dom) code
npm run watch
npm test             # integration test: renders sample.docx/xlsx/pptx in a real VS Code

npm test launches a disposable VS Code instance (@vscode/test-electron), opens each sample with the matching custom editor and waits for the webview to report a successful render. Lifecycle events are also visible at runtime in the Office File Viewer output channel (resolve / rendered / render FAILED / hyperlinks).

Open the project in VS Code and press F5 ("Run Office File Viewer") — a development host opens the samples/ workspace with sample.docx, sample.xlsx and sample.pptx to try.

Package a VSIX with npx @vscode/vsce package (requires npm run package first, which is wired as vscode:prepublish).

Limitations

• Rendering fidelity is defined by the engine; complex documents may differ from Office. See the feature support matrix.
• Large files are loaded fully into memory (bytes are transferred to the webview).
• Rendering runs on the webview's main thread (mode: 'main'); the engine's worker render mode is not used.

Credits

• @silurus/ooxml by Yuki Yokotani — the rendering engine (MIT).
• microsoft/vscode-extension-samples — the custom editor template this extension is modeled on.