Simple OOXML Viewer for VS Code

Open .docx, .xlsx, .pptx and .vsdx files in Visual Studio Code, look at them, change the parts you need to change, and save back into the same file without running them through another program. Every renderer is a WASM engine bundled in the extension; nothing is uploaded and nothing converts on a server.

Offline · No telemetry · No AI · No accounts · No ads

Engines, fonts and WASM assets all ship inside the package. Open / edit / save a file and the extension makes zero network requests: no assistant, no LLM hook, no analytics, no crash reports, no sign-in, no "phone home".

Supported formats

How it works

• Word — the @docx-editor.dev paginated word processor (DOM/ProseMirror), with text shaped through a bundled HarfBuzz WASM asset so line breaks and page breaks match real font metrics. Saving re-zips the OOXML package selectively: parts the editor doesn't understand survive the round-trip untouched.
• Excel — @opencalc/sheet (CasualOffice), a Rust→WASM spreadsheet engine behind a custom element. It owns the file format: open(bytes) and save() go straight through its own .xlsx parser and serializer, so formats, styles, merges, panes and hidden sheets come back unchanged, and inserting or deleting rows rewrites references the way Excel does.
• PowerPoint — the BetterOffice Rust→WASM engine rendered through its React editor.
• Visio — a vendored BetterOffice Rust→WASM diagram core behind a native-feeling canvas shell (the only VS Code extension we know of that opens .vsdx at all).
• Fonts — metric-compatible substitutes (Calibri→Carlito, Cambria→Caladea, Times New Roman→Liberation Serif, Arial→Liberation Sans, Courier New→Liberation Mono, plus Noto Arabic / Hebrew, Gelasio, Inter, Roboto and more) are bundled, so pagination is computed from real metrics without downloading a single face.

Privacy & offline guarantees

No network access. Opening, editing and saving are pure local computation. This is enforced, not just intended:

1. No egress by construction — every engine receives bytes, not URLs. There is no Google Fonts lookup to disable (the API no longer exists in the bundled engine), no CDN fallback, no update checker, no collaboration transport (WebSocket/beacon/EventSource are compile-time forbidden), no AI or "assist" endpoints.
2. Build-time postcheck — every shipped webview bundle is scanned; the build fails if it contains egress markers or collaboration machinery.
3. Strict CSP — the webview runs with script-src 'nonce-…' plus the extension's own cspSource (the Excel engine pulls its UI payload with a dynamic import(), which a nonce cannot cover) and 'wasm-unsafe-eval'; connect-src is limited to the extension's own origin, inside VS Code's sandbox.

No AI. No model calls, no prompts sent anywhere, no third-party inference SDKs, no data sharing. What you open never leaves your machine.

The one deliberate exception: simpleOoxml.cjkFonts: "cdn" (default off) fetches open-licensed CJK font faces from a pinned jsDelivr URL. Off by default, and the only network path the extension can ever take.

Also: macros in .docm/.xlsm/.pptm are never executed; external hyperlinks open through VS Code with an http/https/mailto/tel allowlist only.

Usage

Install and open any supported file — the extension registers as the default editor. Use Open With… to switch back to the binary or text editor at any time.

• Ctrl/Cmd + / - / 0 — zoom in / out / reset
• Ctrl/Cmd S — save (lossless re-zip for Word)
• Ctrl/Cmd F — find in document (where the format supports it)
• Edit the file on disk (e.g. regenerate a report) — the open viewer live-reloads
• Word chrome theme: follow the simpleOoxml.colorMode setting; the document canvas stays Word-faithful white in every mode

Extension settings

Commands

• OOXML Viewer: Show Diagnostics — recent engine lifecycle events, for bug reports
• OOXML Viewer: Copy Diagnostics to Clipboard
• OOXML Viewer: Reload Active Viewer

Known limitations

• Save writes through each engine's serializer; VS Code-level dirty-state markers, hot-exit backup and external-change conflict prompts are planned — until then, undo history lives in the open editor.
• simpleOoxml.initialZoom: "fitPage" currently behaves like width-fit for Word (the bundled engine has no page-height fit target yet).
• Visio: linear fill gradients and arc/gap line jumps render; exotic ShapeSheet features may differ from Visio. .vsdm/.vstx/.vssx and legacy .vsd are not supported.
• CJK text renders with substituted metrics unless simpleOoxml.cjkFonts: "cdn" is enabled.
• Excel: the engine is pinned to @opencalc/sheet@0.0.0. The next tag, 0.0.1, shipped without its editor.core.js chunk (every UI element failed to construct), so the version is exact, not a range. The engine's menu labels are English only, and charts, images, conditional formatting and data validation are previewed as their cached values rather than edited.
• ODF (.odt/.ods/.odp) and legacy binary formats (.doc/.xls/.ppt/.vsd) are not supported.

Development

npm install
npm run compile        # dev build (host + webviews + assets) into out/
npm run watch
npm run typecheck      # host + webview tsc
npm test               # compile + VS Code integration tests (all four formats)
npm run package        # production (minified) build; postchecks enforce the offline contract
npx @vscode/vsce package --no-dependencies   # produce the .vsix
npm run build:vsdx-wasm  # rebuild the vendored Visio WASM (needs the Rust toolchain)

The production build runs a no-egress / no-collaboration postcheck over every shipped bundle and fails the build on violations — the build itself is the enforcement (see the Privacy & offline guarantees section above). docs/SCOPING.md documents the architecture.

.github/workflows/ci.yml runs the host + webview typechecks, the production build (postchecks included), a VSIX pack with a 26 MB size budget, and the VS Code integration suite under Xvfb.

Package size comes mostly from engine WASM and font binaries. One saving is structural: 16 of the Excel engine's 24 fonts (Carlito ×4, Liberation ×12) are byte-identical to the copies already shipped under out/media/assets/, so copyOpencalcAssets() skips them and rewrites those @font-face URLs to ../assets/<name> — 6.76 MB that used to be packed twice. The build also wipes out/media/assets/ before copying, so a retired engine's assets cannot linger in the package.

License & third-party attribution

This project is Apache-2.0 © 2026 wasdzy111. It began as a snapshot of ahati's BetterOffice viewer and has since been rewritten around a different Excel engine; the original author's notice is retained verbatim in NOTICE, as Apache-2.0 requires. The work also builds on open-source engines and fonts; the full, authoritative notices ship inside every package (NOTICE, THIRD-PARTY-NOTICES.md, and the verbatim texts in licenses/ — one folder per bundled package, including the per-family OFL texts). Summary:

The @docx-editor.dev packages are the renamed continuation of the @eigenpal/docx-editor packages (same repository, same Apache-2.0 license); the BetterOffice API design in turn derives from that project. yjs and pdf-lib are declared optional peers of the Word engine for its collaboration and PDF-export entrypoints — this extension ships neither, and they are not bundled.