OOXML Viewer for VS Code

A high-fidelity viewer for .docx, .xlsx, and .pptx files — powered by a Rust/WASM parser and an HTML Canvas renderer.

Private by design. All parsing and rendering happens locally inside the VS Code Webview via WebAssembly. No file contents, no metadata, and no telemetry ever leave your machine. The extension makes no network requests out of the box. Only two strictly opt-in features can cause any outbound request — the MCP server (downloads a binary from GitHub) and Google Fonts substitution (loads metric-compatible fonts from a CDN) — and both are off by default.

Screenshots

DOCX	XLSX	PPTX

Features

• DOCX — Continuous scroll view of every page with a transparent text layer (PDF.js-style) — drag to select, copy as plain text.
• XLSX — Spreadsheet viewer with cell / row / column / range selection, tab-separated copy (Ctrl+C / Cmd+C), freeze-pane support, and a multi-sheet tab bar.
• PPTX — Continuous scroll view of every slide with a transparent text layer that handles rotated text boxes correctly.
• High fidelity — Charts, conditional formatting, theme colors, custom geometry shapes, math equations (OMML, via MathJax + STIX Two Math), and more rendered straight from the OOXML spec.
• MCP server (opt-in) — Lets AI coding agents (Copilot, Claude, etc.) read .xlsx / .docx / .pptx files in your workspace through dedicated tools instead of unzipping XML by hand. See MCP server for AI agents below.

All three formats share the same Rust parser (wasm-pack) for accuracy and speed.

Usage

Open any .docx, .xlsx, or .pptx file in VS Code — the OOXML Viewer takes over as the default editor for those file types.

If a different editor opens by default, right-click the file → Reopen Editor With… → select OOXML Viewer, then optionally Configure default editor to make it the default.

Selection & copy

• DOCX / PPTX — Drag across rendered text to select, then Ctrl+C / Cmd+C to copy as plain text. The transparent overlay matches the canvas glyph positions, so selection feels native. (This dual-layer rendering is planned to be unified once the Canvas drawElement API ships across browsers.)
• XLSX — Click a cell to select it, drag for a range, click row/column headers for full-row/column selection, click the corner box for sheet-wide selection. Ctrl+C / Cmd+C copies as TSV.

MCP server for AI agents

Open a workspace that contains a .xlsx / .docx / .pptx file and the extension offers to enable an MCP server — a tiny native binary that lets AI coding agents read those files directly. Without it, agents typically resort to running unzip + XML parsing in Python; with it, they call typed tools like xlsx_get_cell_range, docx_extract_text, or pptx_get_slide_structure.

• The first time you click Enable, a ~5 MB prebuilt binary is downloaded from this repo's GitHub Releases and verified by SHA256. Subsequent workspaces reuse the cached binary.
• If you already have ooxml-mcp-server on your PATH (e.g. installed via cargo install --git ...), it is used as-is — no download.
• The server is registered with VS Code's MCP API, so any agent that supports MCP (GitHub Copilot Agent mode, Claude, etc.) picks it up automatically.

Settings:

• ooxmlViewer.mcpServer.enabled: auto (default — prompt only when the workspace contains OOXML files), always, or never.
• ooxmlViewer.mcpServer.binaryPath: optional override pointing at a pre-installed binary.

Commands (Command Palette):

• OOXML Viewer: Install / Enable MCP Server
• OOXML Viewer: Disable MCP Server

Font substitution (Google Fonts, opt-in)

Office files often reference fonts that aren't installed on your machine — Calibri, Cambria, and the like. By default the viewer falls back to whatever system font is closest, which can shift line breaks and column widths away from how Word / PowerPoint / Excel would lay the document out.

Enabling ooxmlViewer.useGoogleFonts lets the preview load metric-compatible substitutes from the Google Fonts CDN so the layout matches Office:

• Calibri → Carlito, Cambria → Caladea (same metrics by design).
• Arabic / RTL scripts → Noto Naskh/Sans Arabic.
• A handful of common web fonts (Open Sans, Roboto, Lato, Montserrat, …) when a document asks for them directly.

Network disclosure: when (and only when) this setting is enabled and the workspace is trusted, the preview requests stylesheets from fonts.googleapis.com and font files from fonts.gstatic.com. No file content is ever sent — only the standard font requests a browser makes. The webview's Content-Security-Policy is widened to exactly those two origins solely while the setting is on; with it off, the policy blocks every external origin and the extension stays fully offline.

Settings:

• ooxmlViewer.useGoogleFonts: false (default — fully offline) or true (load metric-compatible fonts from the CDN). Force-disabled in untrusted workspaces. Toggling it re-renders already-open previews immediately.

Privacy & Security

• Local file I/O only. The viewer reads bytes via vscode.workspace.fs.readFile and never writes back — files are opened read-only.
• Webview is offline by default. The Webview's Content Security Policy disallows outbound connections to any origin other than the extension itself. No analytics, no remote API. The only exception is the opt-in Google Fonts substitution: enabling ooxmlViewer.useGoogleFonts widens the CSP to allow fonts.googleapis.com / fonts.gstatic.com and nothing else, and only in trusted workspaces.
• MCP server is opt-in and offline-after-install. Until you accept the install prompt the extension makes no network requests. The download itself only contacts github.com, is checksum-verified, and the resulting binary parses local files only — it does not phone home. Whatever the connected AI agent does with the data is governed by that agent's own privacy settings.
• Open source. Source code at github.com/yukiyokotani/office-open-xml-viewer.

VS Code's own telemetry is independent of this extension and can be controlled via the telemetry.telemetryLevel setting.

Known Limitations

• XLSX: formula evaluation is not yet supported (raw cached values are shown).
• DOCX: image-anchored float wrap, footnotes, and header/footer rendering may differ slightly from Word.
• PPTX: a small number of obscure preset shapes fall back to a rectangle placeholder.
• Media playback (audio / video) is not supported in the Webview.

Issues & Contributions

Report bugs or request features at github.com/yukiyokotani/office-open-xml-viewer/issues.

License

MIT