OpenXML Viewer

A Visual Studio Code extension that lets you preview Office Open XML files (.xlsx / .docx / .pptx) directly inside Visual Studio Code. Just double-click a file to quickly inspect its contents—without launching Excel, Word, or PowerPoint.

[!NOTE] This extension is intended for viewing (read-only). It does not provide editing or saving capabilities.

Table of Contents

• OpenXML Viewer
  • Table of Contents
  • Key Features
  • Supported File Formats
  • Requirements
  • Installation
    • From the Visual Studio Code Marketplace
    • From a VSIX File
  • Usage
  • Commands
  • Copilot Integration
  • Settings
  • Limitations
  • Roadmap
  • Contributing
  • Sponsors
  • License

Key Features

• 📊 View Excel workbooks (.xlsx)
  • Display cell contents in a table, sheet by sheet
  • Switch between multiple sheets with tabs
  • Display merged cells and virtualize rows/columns for responsive scrolling
  • Preserve hidden/styled cells, hyperlinks, themes and style inheritance, ISO dates, scientific/fraction/elapsed-time and conditional number formats
  • Show comments, common conditional formatting/data bars/icon sets, table banding, and cached worksheet charts
  • Keep frozen rows/columns visible, draw numeric line/column/win-loss sparklines, and render cached combination-chart series
  • Keep images visible across worksheet switches and row/column resizing, reflowing two-cell anchors while preserving drawing order
  • Resize column widths and row heights (drag borders, double-click to auto-fit, reset per sheet); adjustments persist across reopen
• 📝 View Word documents (.docx)
  • Display paragraphs, inherited text styles, inline images, headings, and tables
  • Preserve hyperlinks, bookmarks, content controls, tracked insertions/deletions, fields, numbering overrides, table layout/borders/shading/merges, and page sections
  • Render complex field results/fallbacks, page/column breaks, and multi-column section hints
  • Approximate pages around explicit page breaks and display tracked-change author/date metadata
  • Show headers, footers, footnotes, endnotes, and comments as linked auxiliary content
• 📑 View PowerPoint presentations (.pptx)
  • Display text, shapes, and images for each slide
  • Apply per-master themes, nested group rotation/flip transforms, shape/image flips, table merges/styles/borders, fields, and speaker notes
  • Render connectors, cached charts, SmartArt nodes/edges, numeric/formula custom geometry paths, and common effects as bounded SVG/static content
  • Navigate with the slide list or compact previous/next controls
• 🔍 In-viewer text search
  • Run a full-text search over the displayed content and highlight matches
  • Jump to the previous/next match (moving across sheets and slides)
• ♿ Accessible, localized controls
  • English/Japanese UI, a roving ARIA grid with selection state, modal focus management, keyboard navigation/resizing, focus restoration, high-contrast and reduced-motion support
  • Copy focused cells, paragraphs, and slide text with Ctrl/Cmd+C
• ⚡ Manifest-first loading
  • Request worksheet row windows, document chunks, slides, searches, and binary assets from a persistent parser worker only when needed
  • Share one URI-scoped parser worker and bounded caches across split views; file changes invalidate the shared generation once
  • Coalesce equivalent split-view requests, reference-count cancellation, and enforce panel/session/waiter/time limits
  • Patch arriving row windows/document chunks/active slides without rebuilding the whole Webview
• 📤 Static export
  • Export a sanitized self-contained HTML snapshot with no scripts or external resource fetches
  • Assemble sheets, document chunks, and slides cooperatively with cancellation/progress, then export a bounded PDF (up to 100 pages / 100 MiB of validated JPEG data)
• 🩺 Local diagnostics
  • Inspect broker/Worker/Webview cache, index, DOM, Blob, and pending-request counts in an Output channel
  • Diagnostics stay local, contain no document text, and send no telemetry
• 🖱️ Seamless operation
  • Launch the preview simply by opening a file in the Explorer (custom editor)
  • No need to launch external applications
• 🤖 GitHub Copilot integration
  • Contributes language model tools so Copilot can read .docx / .xlsx / .pptx content as Markdown instead of failing on the binary archive
  • Outline, per-format read and search tools, referenced from chat with #officeDocumentOutline, #readWordDocument, #readExcelSheet, #readPowerPointSlides and #searchOfficeDocument
  • Text only: images and embedded binaries are never returned, and only files inside the workspace (or open in an editor) can be read
• 🔒 Safe viewing
  • Read-only, so accidental edits cannot corrupt the file
  • The Webview's Content Security Policy (CSP) restricts loading external resources
  • Supports Restricted Mode and virtual workspaces; files are read only through the VS Code file-system API and no external document resources are fetched

Supported File Formats

[!IMPORTANT] The target is Office Open XML (OOXML) files. Legacy binary formats (.xls / .doc / .ppt) and macro-enabled formats (such as .xlsm) are not supported.

See OOXML Compatibility Matrix for feature-level static rendering and fallback behavior.

Requirements

• Visual Studio Code 1.104.0 or later
• No additional runtime or external application (such as Microsoft Office) is required

Installation

From the Visual Studio Code Marketplace

1. Open the Extensions view from the VS Code sidebar (Ctrl+Shift+X / ⌘+Shift+X)
2. Search for OpenXML Viewer
3. Click Install

From a VSIX File

code --install-extension openxml-viewer-<version>.vsix

Alternatively, open the Command Palette (Ctrl+Shift+P / ⌘+Shift+P), run "Extensions: Install from VSIX...", and select the .vsix file.

Usage

1. Open a .xlsx / .docx / .pptx file in the VS Code Explorer.
2. This extension's custom editor launches automatically and shows a preview of the contents.
3. If you want to open the file in the default text editor or another editor, right-click the file and switch the way it opens via "Open With...".

[!TIP] If you want to change the default way a file opens, you can set the default editor per extension via "Open With..." → "Configure default editor for '*.xlsx'...".

Type a keyword into the search bar at the top of the preview to run a full-text search over the displayed document. Press Enter / Shift+Enter to move to the next / previous match, and Esc to clear the search. For spreadsheets and presentations, the viewer automatically switches to the matching sheet / slide.

Commands

These are available from the Command Palette (Ctrl+Shift+P / ⌘+Shift+P).

Copilot Integration

The extension contributes language model tools so that GitHub Copilot can retrieve information from Office files. Copilot cannot read .docx / .xlsx / .pptx on its own because they are binary ZIP archives; these tools parse them in the extension host and return plain Markdown.

In agent mode the tools are picked automatically. You can also reference them explicitly in a chat prompt with #.

Example prompts:

Summarize #readWordDocument for docs/spec.docx
What is the total in the Budget sheet of data/plan.xlsx?
Find every mention of "deadline" in slides/kickoff.pptx

[!NOTE] The tools are read-only and offline. They return text only — images and embedded binaries are never sent to the model — and they refuse paths outside the open workspace folders unless the file is already open in an editor. Long documents are truncated to a character budget, and the response states how to request the next range.

Settings

You can configure these in settings.json (user settings / workspace settings).

Example configuration:

{
  "openxmlViewer.spreadsheet.maxRows": 5000,
  "openxmlViewer.theme": "dark"
}

Limitations

[!WARNING] This extension is intended to provide a simple preview. It does not guarantee rendering that is fully compatible with Excel, Word, or PowerPoint. The layout, formatting, colors, and so on may differ from how the file appears in the original Office application.

• Editing or saving Office content is not supported (view-only). HTML/PDF export creates a static viewer representation and does not modify the source.
• Charts, SmartArt, custom geometry, conditional formatting, and other advanced objects may use a simplified static fallback rather than Office-identical rendering.
• Cached chart series (including common combination charts), legends/axes/data labels, simple stacked charts, SmartArt data edges, and common custom-geometry formulas/arcs are rendered; complex effects/layout rules and exact Word pagination remain approximations.
• Frozen spreadsheet panes and numeric line/column/win-loss sparklines are rendered. Split panes, filters, data validation, print metadata, Word first/even/default section references, anchored-object metadata, text boxes, and richer field fallbacks remain static hints/approximations.
• PDF output is intentionally viewer-static and is not guaranteed to match Microsoft Office pagination or fonts.
• Hyperlinks are opened only after user interaction and only for http, https, or mailto; embedded external resources are never fetched by the preview.
• Embedded images are limited to safe raster MIME types (PNG, JPEG, GIF, BMP, WebP); SVG/vector/unknown image payloads are not expanded or embedded in exports.
• Raster signatures and decoded dimensions/pixel counts are validated, while ZIP, asset, search, and warm-session caches are byte bounded.
• Password-protected or encrypted files cannot be opened.
• Content beyond the parser's safety budgets (rows, blocks, slides, objects, or table cells) is omitted with an in-viewer notice.
• Formulas display their cached result values (no recalculation is performed).
• The Copilot language model tools return text only. Images, charts, and embedded binaries are never sent to the model, layout and styling are not preserved, and long documents are truncated to a character budget.
• Legacy binary formats (.xls / .doc / .ppt) are not supported.

Roadmap

• [x] .xlsx viewer (cells, multiple sheets)
• [x] .docx viewer (body, tables, images)
• [x] .pptx viewer (slides, thumbnails)
• [x] In-viewer text search (match highlighting, previous/next navigation)
• [x] Resizable spreadsheet column widths and row heights (drag, auto-fit, persistence)
• [x] Keyboard text/cell copy support
• [x] Bounded cached chart, SmartArt, connector, and custom-geometry rendering
• [x] Shared parser sessions and incremental lazy rendering
• [x] Sanitized self-contained HTML and bounded static PDF export
• [x] Shared request QoS, cooperative search/export, count-only local diagnostics, and reproducible release metadata
• [x] Clean-checkout builds, Webview epochs/Worker recovery, full-vs-lazy parity, byte/pixel budgets, internal workbook/slide navigation, and installed-VSIX validation

Contributing

Bug reports, feature requests, and pull requests are welcome. Feel free to reach out via Issues.

For specifications, design, and build/debug instructions, see DEVELOPMENT.md. For publishing to the Marketplace, see PUBLISHING.md.

Sponsors

If you would like to support the development of this project, contributions via GitHub Sponsors are welcome. Your support will be used to improve features and maintain the project over time.

License

This project is released under the MIT License.